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Unpaid losses and loss expenses
 12 Months Ended
Dec. 31, 2023
Liability for Claims and Claims Adjustment Expense [Abstract]  
Unpaid Losses and Loss Expenses
Chubb establishes reserves for the estimated unpaid ultimate liability for losses and loss expenses under the terms of its policies and agreements. Reserves include estimates for both claims that have been reported and for IBNR claims, and include estimates of expenses associated with processing and settling these claims. Reserves are recorded in Unpaid losses and loss expenses in the Consolidated balance sheets. While we believe that our reserves for unpaid losses and loss expenses at December 31, 2023, are adequate, new information or trends may lead to future developments in incurred loss and loss expenses significantly greater or less than the reserves provided. Any such revisions could result in future changes in estimates of losses or reinsurance recoverable and would be reflected in our results of operations in the period in which the estimates are changed.
The following table presents a reconciliation of beginning and ending Unpaid losses and loss expenses:
Year Ended December 31
(in millions of U.S. dollars)202320222021
Gross unpaid losses and loss expenses, beginning of year$75,747 $72,330 $67,192 
Reinsurance recoverable on unpaid losses (1)
(17,086)(16,132)(14,576)
Net unpaid losses and loss expenses, beginning of year58,661 56,198 52,616 
Net losses and loss expenses incurred in respect of losses occurring in:
Current year24,956 23,680 21,986 
Prior years (2)
(856)(1,108)(956)
Total24,100 22,572 21,030 
Net losses and loss expenses paid in respect of losses occurring in:
Current year8,248 7,331 6,900 
Prior years12,763 12,206 10,048 
Total21,011 19,537 16,948 
Consolidation of Huatai Group
405 — — 
Foreign currency revaluation and other83 (572)(500)
Net unpaid losses and loss expenses, end of year62,238 58,661 56,198 
Reinsurance recoverable on unpaid losses (1)
17,884 17,086 16,132 
Gross unpaid losses and loss expenses, end of year$80,122 $75,747 $72,330 
(1)     Net of valuation allowance for uncollectible reinsurance.
(2)    Relates to prior period loss reserve development only and excludes prior period development related to reinstatement premiums, expense adjustments, earned premiums, and A&H long-duration lines totaling $83 million, $232 million, and $30 million for 2023, 2022, and 2021, respectively.

The increase in gross and net unpaid losses and loss expense in 2023 reflects underlying exposure growth and the consolidation of Huatai, partially offset by favorable prior period development. The increase in gross and net unpaid losses and loss expense in 2022 is due to an increase in underlying exposure due to premium growth, increased loss severity trends and net catastrophe losses, partially offset by favorable prior period development, and favorable foreign exchange movement.

The loss development tables under section c) below, present Chubb’s historical incurred and paid claims development by broad product line through December 31, 2023, net of reinsurance, as well as the cumulative number of reported claims, IBNR balances, and other supplementary information.

Recent period inflation is higher than the levels underlying our loss development triangles. To account for this, our loss estimates for a number of product lines include explicit adjustments by accident year for the potential increase in ultimate claim severity.
The following table presents a reconciliation of the loss development tables to the liability for unpaid losses and loss expenses in the consolidated balance sheet:

Reconciliation of Reserve Balances to Liability for Unpaid Loss and Loss Expenses
(in millions of U.S. dollars)December 31, 2023
Presented in the loss development tables:
  North America Commercial P&C Insurance — Workers' Compensation$10,159 
  North America Commercial P&C Insurance — Liability21,092 
  North America Commercial P&C Insurance — Other Casualty2,596 
  North America Commercial P&C Insurance — Non-Casualty3,203 
  North America Personal P&C Insurance3,550 
  Overseas General Insurance — Casualty8,157 
  Overseas General Insurance — Non-Casualty3,515 
  Global Reinsurance — Casualty1,240 
  Global Reinsurance — Non-Casualty411 
Excluded from the loss development tables:
  Other6,286 
Net unpaid loss and allocated loss adjustment expense60,209 
Ceded unpaid loss and allocated loss adjustment expense:
  North America Commercial P&C Insurance — Workers' Compensation1,190 
  North America Commercial P&C Insurance — Liability7,427 
  North America Commercial P&C Insurance — Other Casualty1,064 
  North America Commercial P&C Insurance — Non-Casualty1,673 
  North America Personal P&C Insurance577 
  Overseas General Insurance — Casualty2,527 
  Overseas General Insurance — Non-Casualty1,736 
  Global Reinsurance — Casualty80 
  Global Reinsurance — Non-Casualty101 
  Other1,781 
Ceded unpaid loss and allocated loss adjustment expense18,156 
Unpaid unallocated loss adjustment expenses1,757 
Unpaid losses and loss expenses$80,122 
Business excluded from the loss development tables
“Other” shown in the reconciliation table comprises businesses excluded from the loss development tables:
•Corporate segment business, which includes run-off liabilities such as asbestos, environmental, and molestation and other mass tort exposures and which impact accident years older than those shown in the loss development tables;
•North America Agricultural Insurance segment business, which is short-tailed with the majority of the liabilities expected to be resolved in the ensuing twelve months; and
•Certain subsets of our business due to data limitations or unsuitability to the loss development table presentation, including:
•Various loss portfolio transfers; by convention, all premium and losses associated with these transactions are recorded to the policy period of the transaction, even though the accident dates of the claims covered may be a decade or more in the past. We also underwrite certain high attachment, high limit, multiple-line and excess of aggregate coverages for large commercial clients. Changes in incurred loss and cash flow patterns are volatile and sufficiently different from those of typical insureds. This category includes the Alternative Risk Solutions business within the North America Commercial P&C Insurance segment;
•2015 and prior paid history on a subset of previously acquired international businesses, within the Overseas General Insurance segment, due to limitations on the data prior to the acquisition;
•Huatai P&C business and International A&H lines, where incurred loss development is shorter-tailed than the majority of the liabilities in the Overseas General segment and reported claims are high frequency and low severity in nature;
•Purchase accounting adjustments related to unpaid losses and loss expenses for Chubb Corp;
•Reinsurance recoverable bad debt; and
•Balances with insufficient detail.

a) Description of Reserving Methodologies
Our recorded reserves represent management's best estimate of the provision for unpaid claims as of the balance sheet date. The process of establishing loss and loss expense reserves can be complex and is subject to considerable uncertainty as it requires the use of estimates and judgments based on circumstances underlying the insured loss at the date of accrual. The reserves for our various product lines each require different qualitative and quantitative assumptions and judgments to be made. Management's best estimate is developed after collaboration with actuarial, underwriting, claims, legal, and finance departments and culminates with the input of reserve committees. Each business unit reserve committee includes the participation of the relevant parties from actuarial, finance, claims, and unit senior management and has the responsibility for finalizing, recommending and approving the estimate to be used as management's best estimate. Reserves are further reviewed by Chubb's Chief Actuary and senior management. The objective of such a process is to determine a single estimate that we believe represents a better estimate than any other and which is viewed by management to be the best estimate of ultimate loss settlements. This estimate is based on a combination of exposure and experience-based actuarial methods (described below) and other considerations such as claims reviews, reinsurance recovery assumptions and/or input from other knowledgeable parties such as underwriting. Exposure-based methods are most commonly used on relatively immature origin years (i.e., the year in which the losses were incurred — “accident year” or “report year”), while experience-based methods provide a view based on the projection of loss experience that has emerged as of the valuation date. Greater reliance is placed upon experience-based methods as the pool of emerging loss experience grows and where it is deemed sufficiently credible and reliable as the basis for the estimate. In comparing the held reserve for any given origin year to the actuarial projections, judgment is required as to the credibility, uncertainty and inherent limitations of applying actuarial techniques to historical data to project future loss experience. Examples of factors that impact such judgments include, but are not limited to, the following:

•nature and complexity of underlying coverage provided and net limits of exposure provided;
•segmentation of data to provide sufficient homogeneity and credibility for loss projection methods;
•extent of credible internal historical loss data and reliance upon industry information as required;
•historical variability of actual loss emergence compared with expected loss emergence;
•reported and projected loss trends;
•extent of emerged loss experience relative to the remaining expected period of loss emergence;
•rate monitor information for new and renewal business;
•changes in claims handling practice;
•inflation;
•the legal environment;
•facts and circumstances of large claims;
•terms and conditions of the contracts sold to our insured parties;
•impact of applicable reinsurance recoveries; and
•nature and extent of underlying assumptions.
We have actuarial staff within each of our business units who analyze loss reserves (including loss expenses) and regularly project estimates of ultimate losses and the corresponding indications of the required IBNR reserve. Our reserving approach is a comprehensive ground-up process using data at a detailed level that reflects the specific types and coverages of the diverse products written by our various operations. The data presented in this disclosure was prepared on a more aggregated basis and with a focus on changes in incurred loss estimates over time as well as associated cash flows. We note that data prepared on this basis may not demonstrate the full spectrum of characteristics that are evident in the more detailed level studied internally.

We perform an actuarial reserve review for each product line at least once a year. For most product lines, one or more standard actuarial reserving methods may be used to determine estimates of ultimate losses and loss expenses, and from these estimates, a single actuarial central estimate is selected. The actuarial central estimate is an input to the reserve committee process described above. For the few product lines that do not lend themselves to standard actuarial reserving methods, appropriate techniques are applied to produce the actuarial central estimates. For example, run-off asbestos and environmental liability estimates are better suited to the application of account-specific exposure-based analyses to best evaluate their associated aggregate reserve levels.

b) Standard actuarial reserving methods
The judgments involved in projecting the ultimate losses include the use and interpretation of various standard actuarial reserving methods that place reliance on the extrapolation of actual historical data, loss development patterns, industry data, and other benchmarks as appropriate.

Standard actuarial reserving methods include, but are not limited to, expected loss ratio, paid and reported loss development, and Bornhuetter-Ferguson methods. A general description of these methods is provided below. In addition to these standard methods, depending upon the product line characteristics and available data, we may use other recognized actuarial methods and approaches. Implicit in the standard actuarial methods that we generally utilize is the need for two fundamental assumptions: first, the pattern by which losses are expected to emerge over time for each origin year, and second, the expected loss ratio for each origin year.

The expected loss ratio for any particular origin year is selected after consideration of a number of factors, including historical loss ratios adjusted for rate changes, premium and loss trends, industry benchmarks, the results of policy level loss modeling at the time of underwriting, and/or other more subjective considerations for the product line (e.g., terms and conditions) and external environment as noted above. The expected loss ratio for a given origin year is initially established at the start of the origin year as part of the planning process. This analysis is performed in conjunction with underwriters and management. The expected loss ratio method arrives at an ultimate loss estimate by multiplying the expected ultimate loss ratio by the corresponding premium base. This method is most commonly used as the basis for the actuarial central estimate for immature origin periods on product lines where the actual paid or reported loss experience is not yet deemed sufficiently credible to serve as the principal basis for the selection of ultimate losses. The expected loss ratio for a given origin year may be modified over time if the underlying assumptions differ from the original assumptions (e.g., the assessment of prior year loss ratios, loss trend, rate changes, actual claims, or other information).

Our selected paid and reported development patterns provide a benchmark against which the actual emerging loss experience can be monitored. Where possible, development patterns are selected based on historical loss emergence by origin year. For product lines where the historical data is viewed to have low statistical credibility, the selected development patterns also reflect relevant industry benchmarks and/or experience from similar product lines written elsewhere within Chubb. This most commonly occurs for relatively new product lines that have limited historical data or for high severity/low frequency portfolios where our historical experience exhibits considerable volatility and/or lacks credibility. The paid and reported loss development methods convert the selected loss emergence pattern to a set of multiplicative factors which are then applied to actual paid or reported losses to arrive at an estimate of ultimate losses for each period. Due to their multiplicative nature, the paid and reported loss development methods will leverage differences between actual and expected loss emergence. These methods tend to be utilized for more mature origin periods and for those portfolios where the loss emergence has been relatively consistent over time.

The Bornhuetter-Ferguson method is a combination of the expected loss ratio method and the loss development method, where the loss development method is given more weight as the origin year matures. This approach allows a logical transition between the expected loss ratio method which is generally utilized at earlier maturities and the loss development methods which are typically utilized at later maturities. We usually apply this method using reported loss data although paid data may also be used.
Short-tail business
Short-tail business generally describes product lines for which losses are typically known and paid shortly after the loss occurs. This would include, for example, most property, personal accident, and automobile physical damage policies that we write. Due to the short reporting and development pattern for these product lines, the uncertainty associated with our estimate of ultimate losses for any particular accident period diminishes relatively quickly as actual loss experience emerges. We typically assign credibility to methods that incorporate actual loss emergence, such as the paid and reported loss development and Bornhuetter-Ferguson methods, sooner than would be the case for long-tail lines at a similar stage of development for a given origin year. The reserving process for short-tail losses arising from catastrophic events typically involves an assessment by the claims department, in conjunction with underwriters and actuaries, of our exposure and estimated losses immediately following an event and then subsequent revisions of the estimated losses as our insureds provide updated actual loss information.

Long-tail business
Long-tail business describes lines of business for which specific losses may not be known/reported for some period and for which claims can take significant time to settle/close. This includes most casualty lines such as general liability, D&O, and workers' compensation. There are various factors contributing to the uncertainty and volatility of long-tail business, including the indirect impact of COVID-19 that has changed loss reporting and development patterns. In addition, uncertain future inflationary trends, changes in future legal environments, and the potential impact of major claims, such as molestation claims including the Boy Scouts of America (BSA) agreement-in-principle, added to the uncertainty and volatility in the long-tail business. Other factors are:
•The nature and complexity of underlying coverage provided and net limits of exposure provided;
•Our historical loss data and experience is sometimes too immature and lacking in credibility to rely upon for reserving purposes. Where this is the case, in our reserve analysis we may utilize industry loss ratios or industry benchmark development patterns that we believe reflect the nature and coverage of the underwritten business and its future development, where available. For such product lines, actual loss experience may differ from industry loss statistics as well as loss experience for previous underwriting years;
•The difficulty in estimating loss trends, claims inflation (e.g., medical and judicial) and underlying economic conditions;
•The need for professional judgment to estimate loss development patterns beyond that represented by historical data using supplemental internal or industry data, extrapolation, or a blend of both;
•The need to address shifts in business mix or volume over time when applying historical paid and reported loss development patterns from older origin years to more recent origin years. For example, changes over time in the processes and procedures for establishing case reserves can distort reported loss development patterns or changes in ceded reinsurance structures by origin year can alter the development of paid and reported losses;
•Loss reserve analyses typically require loss or other data be grouped by common characteristics in some manner. If data from two combined lines of business exhibit different characteristics, such as loss payment patterns, the credibility of the reserve estimate could be affected. Additionally, since casualty lines of business can have significant intricacies in the terms and conditions afforded to the insured, there is an inherent risk as to the homogeneity of the underlying data used in performing reserve analyses; and
•The applicability of the price change data used to estimate ultimate loss ratios for most recent origin years.

As described above, various factors are considered when determining appropriate data, assumptions, and methods used to establish the loss reserve estimates for long-tail product lines. These factors may also vary by origin year for given product lines. The derivation of loss development patterns from data and the selection of a tail factor to project ultimate losses from actual loss emergence require considerable judgment, particularly with respect to the extent to which historical loss experience is relied upon to support changes in key reserving assumptions.
c) Loss Development Tables
The tables were designed to present business with similar risk characteristics which exhibit like development patterns and generally similar trends, in order to provide insight into the nature, amount, timing and uncertainty of cash flows related to our claims liabilities.

Each table follows a similar format and reflects the following:
•The incurred loss triangle includes both reported case reserves and IBNR liabilities.
•Both the incurred and paid loss triangles include allocated loss adjustment expense (i.e., defense and investigative costs particular to individual claims) but exclude unallocated loss adjustment expense (i.e., the costs associated with internal claims staff and third-party administrators).
•The amounts in both triangles for the years ended December 31, 2014, to December 31, 2022, and average historical claim duration as of December 31, 2023, are presented as supplementary information.
•All data presented in the triangles is net of reinsurance recoverables.
•The IBNR reserves shown to the right of each incurred loss development exhibit reflect the net IBNR recorded as of December 31, 2023.
•The tables are presented retrospectively with respect to acquisitions where these are material and doing so is practicable. Most notably, the Chubb Corp acquisition is presented retrospectively. The unaudited consolidated data is presented solely for informational purposes and is not necessarily indicative of the consolidated data that might have been observed had the transactions been completed prior to the date indicated.

Historical dollar amounts are presented in this footnote on a constant-dollar basis, which is achieved by assuming constant foreign exchange rates for all periods in the loss triangles, translating prior period amounts using the same local currency exchange rates as the current year end. The impact of this conversion is to show the change between periods exclusive of the effect of fluctuations in exchange rates, which would otherwise distort the change in incurred loss and cash flow patterns shown. The change in incurred loss shown will differ from other U.S. GAAP disclosures of incurred prior period reserve development amounts, which include the effect of fluctuations in exchanges rates.

We provided guidance above on key assumptions that should be considered when reviewing this disclosure and information relating to how loss reserve estimates are developed. We believe the information provided in the “Loss Development Tables” section of the disclosure is of limited use for independent analysis or application of standard actuarial estimations.

Cumulative Number of Reported Claims
Reported claim counts, on a cumulative basis, are provided to the far right of each incurred loss development table. In our North America segments, we generally consider a reported claim to be one claim per coverage per claimant. In our Overseas General Insurance segment, we generally consider a reported claim to be on a per occurrence basis. Global Reinsurance segment’s portfolio comprises a mix of proportional and non-proportional treaties. The proportional treaties are reported on a bulk basis and do not lend themselves to meaningful claim count data. As such, we do not provide claim count information for our Global Reinsurance segment.

We exclude claims closed without payment. Claims are counted on a direct basis without consideration of ceded reinsurance. Use of the presented claim counts in analysis of company experience has significant limitations, including:
•Claims for certain events and/or product lines, such as portions of our A&H business, are not reported on an individual basis, but rather in bulk and thus not available for inclusion in this disclosure.
•Each segment typically has a mixture of primary and excess experience which has shifted over time.
•Captive business, especially in Workers' Compensation and Liability, largely represents fronted business where our net exposure to loss is minimal; however, since the claim count is based on direct claims, there is a mismatch between direct claims and net loss dollars, the extent of which varies by accident year.

Reported claim counts include open claims which have case reserves but exclude claims that have been incurred but not reported. As such the reported claims are not consistent with the incurred losses in the triangle, which include incurred but not reported losses. One can calculate reported losses by subtracting incurred but not reported losses from incurred losses in the triangle. Reported claim counts are also inconsistent with losses in the paid loss triangle, since reported counts would include claims with case reserves but no payments to date.
North America Commercial P&C Insurance — Workers' Compensation — Long-tail
This product line has a broad mix of exposures across industries as well as a mix of policy coverages. Types of coverage include risk management business predominantly with high deductible policies, loss sensitive business (i.e., retrospectively-rated policies), business fronted for captives, as well as excess and primary guaranteed cost coverages.

The triangle below shows all loss and allocated expense development for the workers' compensation product line. In our prior period development disclosure, we exclude any loss development where there is a directly related premium adjustment. For workers' compensation, changes in the exposure base due to payroll audits will drive changes in ultimate losses. In addition, we record involuntary pool assumptions (premiums and losses) on a lagged basis. Both of these items will influence the development in the triangle, particularly the first prior accident year, and are included in the reconciliation table presented on page F-66.
Net Incurred Loss and Allocated Loss Adjustment Expenses
Years Ended December 31 As of December 31 2023
(in millions of U.S. dollars)UnauditedNet IBNR Reserves
Reported Claims (in thousands)
Accident Year2014201520162017201820192020202120222023
2014$1,207 $1,201 $1,217 $1,215 $1,163 $1,100 $1,073 $1,037 $1,007 $983 $236 45 
20151,282 1,259 1,276 1,279 1,217 1,154 1,128 1,092 1,057 286 50 
20161,366 1,361 1,383 1,378 1,269 1,206 1,177 1,162 354 51 
20171,412 1,380 1,399 1,393 1,376 1,176 1,121 402 50 
20181,359 1,361 1,380 1,385 1,384 1,221 435 51 
20191,391 1,384 1,400 1,409 1,406 611 48 
20201,367 1,388 1,409 1,408 756 31 
20211,348 1,330 1,372 708 35 
20221,344 1,407 835 38 
20231,371 992 33 
Total$12,508 
Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
(in millions of U.S. dollars)Unaudited
Accident Year2014201520162017201820192020202120222023
2014$113 $295 $410 $484 $532 $566 $599 $617 $634 $649 
2015116 301 418 501 564 606 628 645 665 
2016122 326 452 529 584 621 653 683 
2017120 313 437 516 564 601 626 
2018130 329 451 528 597 641 
2019143 341 467 575 640 
2020111 282 390 466 
2021120 331 458 
2022131 332 
2023129 
Total$5,289 
Net Liabilities for Loss and Allocated Loss Adjustment Expenses
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$2,940 
Accident years 2014 - 2023 from tables above7,219 
All Accident years$10,159 
North America Commercial P&C Insurance — Workers' Compensation — Long-tail (continued)
Supplementary Information: (Favorable)/ Adverse Prior Period Development
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$(113)
Accident years 2014 - 2023 from tables above(191)
All Accident years$(304)
Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2023 (Unaudited)
Age in Years1 2 3 4 5 6 7 8 9 10 
Percentage10 %16 %10 %7 %5 %3 %3 %2 %2 %2 %

North America Commercial P&C Insurance — Liability — Long-tail
This line consists of primary and excess general liability exposures, medical liability, and professional lines, including directors and officers (D&O) liability, errors and omissions (E&O) liability, employment practices liability (EPL), fidelity bonds, and fiduciary liability.

The primary and excess general liability business represents the largest part of these exposures. The former includes both monoline and commercial package liability. The latter includes a substantial proportion of commercial umbrella, excess and high excess business, where loss activity can produce significant volatility in the loss triangles at later ages within an accident year (and sometimes across years) due to the size of the limits afforded and the complex nature of the underlying losses.

This line includes management and professional liability products provided to a wide variety of clients, from national accounts to small firms along with private and not-for-profit organizations, distributed through brokers, agents, wholesalers, and MGAs. Many of these coverages, particularly D&O and E&O, are typically written on a claims-made form. While most of the coverages are underwritten on a primary basis, there are significant amounts of excess exposure with large policy limits.

Net Incurred Loss and Allocated Loss Adjustment Expenses
Years Ended December 31As of December 31 2023
(in millions of U.S. dollars)UnauditedNet IBNR Reserves
Reported Claims (in thousands)
Accident Year2014201520162017201820192020202120222023
2014$3,528 $3,578 $3,667 $3,710 $3,649 $3,463 $3,340 $3,192 $3,142 $3,134 $237 24 
20153,552 3,701 3,810 3,967 3,934 3,727 3,701 3,569 3,613 358 27 
20163,527 3,588 3,685 3,797 3,793 3,765 3,756 3,660 375 27 
20173,316 3,491 3,573 3,623 3,545 3,434 3,492 603 26 
20183,368 3,485 3,688 3,820 3,900 3,915 672 28 
20193,446 3,620 3,858 4,050 4,057 1,135 29 
20204,102 3,826 3,919 3,976 1,630 24 
20214,315 4,349 4,441 2,589 25 
20224,561 4,567 3,371 25 
20234,703 4,181 26 
Total$39,558 
North America Commercial P&C Insurance — Liability — Long-tail (continued)
Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
(in millions of U.S. dollars)Unaudited
Accident Year2014201520162017201820192020202120222023
2014$164 $679 $1,248 $1,801 $2,199 $2,439 $2,580 $2,669 $2,753 $2,802 
2015138 604 1,203 1,852 2,287 2,527 2,743 2,921 3,079 
2016171 662 1,334 1,973 2,332 2,593 2,820 2,982 
2017161 616 1,160 1,698 2,000 2,322 2,627 
2018189 753 1,301 1,773 2,335 2,782 
2019175 669 1,245 1,888 2,387 
2020152 589 1,148 1,697 
2021174 609 1,200 
2022144 649 
2023197 
Total$20,402 
Net Liabilities for Loss and Allocated Loss Adjustment Expenses
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$1,936 
Accident years 2014 - 2023 from tables above19,156 
All Accident years$21,092 
Supplementary Information: (Favorable)/ Adverse Prior Period Development
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$47 
Accident years 2014 - 2023 from tables above175 
All Accident years$222 
Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2023 (Unaudited)
Age in Years1 2 3 4 5 6 7 8 9 10 
Percentage4 %13 %15 %16 %12 %8 %6 %4 %4 %2 %
North America Commercial P&C Insurance — Other Casualty — Long-tail
This product line consists of the remaining commercial casualty coverages such as automobile liability and aviation as well as our foreign casualty exposures (mainly auto, general liability and employer responsibility coverages) on U.S.-based multinational accounts. The paid and reported data are impacted by some catastrophe loss activity.
Net Incurred Loss and Allocated Loss Adjustment Expenses
Years Ended December 31As of December 31 2023
(in millions of U.S. dollars)UnauditedNet IBNR Reserves
Reported Claims (in thousands)
Accident Year2014201520162017201820192020202120222023
2014$594 $582 $580 $595 $554 $538 $538 $530 $526 $530 $9 17 
2015486 469 500 514 457 454 462 457 456 18 15 
2016503 501 527 523 480 479 469 473 20 16 
2017531 565 577 616 604 590 602 16 17 
2018535 563 574 579 575 606 9 17 
2019606 636 686 744 756 40 17 
2020640 633 657 638 156 11 
2021675 710 747 254 13 
2022782 801 367 14 
2023844 631 11 
Total$6,453 
Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
(in millions of U.S. dollars)Unaudited
Accident Year2014201520162017201820192020202120222023
2014$80 $220 $317 $391 $454 $473 $500 $508 $513 $517 
201547 137 214 304 370 394 411 423 431 
201652 145 246 323 374 398 424 437 
201766 175 312 381 446 496 539 
201874 169 270 365 472 532 
201970 189 318 465 619 
202054 156 273 401 
202160 176 293 
202282 235 
202381 
Total$4,085 
Net Liabilities for Loss and Allocated Loss Adjustment Expenses
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$228 
Accident years 2014 - 2023 from tables above
2,368 
All Accident years$2,596 
North America Commercial P&C Insurance — Other-Casualty — Long-tail (continued)
Supplementary Information: (Favorable)/ Adverse Prior Period Development
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$(6)
Accident years 2014 - 2023 from tables above
99 
All Accident years$93 
Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2023 (Unaudited)
Age in Years1 2 3 4 5 6 7 8 9 10 
Percentage10 %18 %18 %17 %15 %7 %6 %2 %1 %1 %

North America Commercial P&C Insurance — Non-Casualty — Short-tail
This product line represents first party commercial product lines that are short-tailed in nature, such as property, inland marine, ocean marine, surety, and A&H. There is a wide diversity of products, primary and excess coverages, and policy sizes. During this ten-year period, this product line was impacted by natural catastrophes mainly in the 2017 and 2018 accident years, and in accident year 2020 by direct COVID.
Net Incurred Loss and Allocated Loss Adjustment Expenses
Years Ended December 31As of December 31 2023
(in millions of U.S. dollars)UnauditedNet IBNR Reserves
Reported Claims (in thousands)
Accident Year2014201520162017201820192020202120222023
2014$1,635 $1,655 $1,573 $1,552 $1,543 $1,544 $1,552 $1,545 $1,544 $1,554 $— 483 
20151,731 1,740 1,645 1,633 1,600 1,585 1,587 1,592 1,589 2 545 
20161,904 1,884 1,794 1,775 1,811 1,824 1,820 1,822 23 650 
20172,699 2,603 2,503 2,520 2,512 2,522 2,508 43 764 
20182,047 2,234 2,169 2,161 2,170 2,160 11 904 
20192,046 2,031 1,954 1,944 1,921 13 1,044 
20203,140 2,942 2,726 2,685 62 1,126 
20212,941 2,824 2,628 158 863 
20223,048 2,946 371 897 
20233,072 1,351 756 
Total$22,885 
Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
(in millions of U.S. dollars)Unaudited
Accident Year2014201520162017201820192020202120222023
2014$816 $1,368 $1,478 $1,499 $1,525 $1,540 $1,547 $1,552 $1,552 $1,551 
2015724 1,339 1,484 1,552 1,567 1,570 1,583 1,582 1,583 
2016844 1,499 1,650 1,726 1,754 1,778 1,789 1,790 
2017977 2,083 2,301 2,392 2,406 2,430 2,449 
20181,025 1,821 2,012 2,068 2,113 2,137 
20191,028 1,672 1,800 1,856 1,883 
20201,390 2,260 2,466 2,545 
20211,085 2,100 2,322 
20221,050 2,190 
20231,219 
Total$19,669 
North America Commercial P&C Insurance — Non-Casualty — Short-tail (continued)
Net Liabilities for Loss and Allocated Loss Adjustment Expenses
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$(13)
Accident years 2014 - 2023 from tables above
3,216 
All Accident years$3,203 
Supplementary Information: (Favorable)/ Adverse Prior Period Development
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$(4)
Accident years 2014 - 2023 from tables above
(377)
All Accident years$(381)

Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2023 (Unaudited)
Age in Years1 2 3 4 5 6 7 8 9 10 
Percentage44 %37 %8 %3 %1 %1 %1 %— %— %— %

North America Personal P&C Insurance — Short-tail
Chubb provides personal lines coverages for high-net-worth individuals and families in North America including homeowners, automobile, valuable articles (including fine art), umbrella liability, and recreational marine insurance offered through independent regional agents and brokers. During this ten-year period, this segment was also impacted by natural catastrophes, mainly in the 2017 and 2018 accident years.
Net Incurred Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
As of December 31 2023
(in millions of U.S. dollars)UnauditedNet IBNR Reserves
Reported Claims (in thousands)
Accident Year2014201520162017201820192020202120222023
2014$2,198 $2,199 $2,186 $2,139 $2,153 $2,140 $2,135 $2,134 $2,133 $2,130 $6 144 
20152,488 2,543 2,553 2,536 2,556 2,562 2,559 2,561 2,558 5 148 
20162,433 2,529 2,538 2,476 2,464 2,458 2,466 2,467 10 154 
20173,028 3,062 2,995 2,991 2,992 3,001 3,011 20 163 
20183,002 3,030 3,095 3,110 3,131 3,120 45 170 
20192,949 2,985 2,986 2,978 2,957 48 157 
20202,922 2,627 2,626 2,582 96 123 
20213,027 2,877 2,964 209 131 
20223,102 2,955 414 119 
20233,406 1,480 93 
Total$28,150 
North America Personal P&C Insurance — Short-tail (continued)
Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
(in millions of U.S. dollars)Unaudited
Accident Year2014201520162017201820192020202120222023
2014$1,306 $1,759 $1,919 $2,028 $2,073 $2,100 $2,109 $2,116 $2,119 $2,121 
20151,495 2,078 2,264 2,385 2,472 2,501 2,526 2,535 2,542 
20161,449 2,046 2,205 2,308 2,364 2,391 2,422 2,440 
20171,694 2,514 2,662 2,793 2,864 2,930 2,971 
20181,922 2,542 2,699 2,857 2,971 3,037 
20191,664 2,431 2,611 2,718 2,823 
20201,331 1,990 2,223 2,363 
20211,583 2,368 2,582 
20221,411 2,278 
20231,490 
Total$24,647 
Net Liabilities for Loss and Allocated Loss Adjustment Expenses
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$47 
Accident years 2014 - 2023 from tables above
3,503 
All Accident years$3,550 
Supplementary Information: (Favorable)/ Adverse Prior Period Development
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$3 
Accident years 2014 - 2023 from tables above
(131)
All Accident years$(128)
Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2023 (Unaudited)
Age in Years1 2 3 4 5 6 7 8 9 10 
Percentage55 %25 %7 %5 %3 %2 %1 %— %— %— %
Overseas General Insurance — Casualty — Long-tail
This product line comprises D&O liability, E&O liability, financial institutions (including crime/fidelity coverages), and non-U.S. general liability as well as aviation and political risk. Exposures are located around the world, including Europe, Latin America, and Asia. Approximately 46 percent of Chubb Overseas General business is generated by European accounts, exclusive of Lloyd's market. There is some U.S. exposure in Casualty from multinational accounts and in financial lines for Lloyd's market. The financial lines coverages are typically written on a claims-made form, while general liability coverages are typically on an occurrence basis and comprises a mix of primary and excess businesses.

Net Incurred Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
As of December 31 2023
(in millions of U.S. dollars)UnauditedNet IBNR Reserves
Reported Claims (in thousands)
Accident Year2014201520162017201820192020202120222023
2014$1,196 $1,264 $1,271 $1,290 $1,210 $1,129 $1,093 $1,103 $1,106 $1,089 $46 38 
20151,118 1,209 1,239 1,262 1,244 1,186 1,171 1,187 1,186 97 40 
20161,150 1,246 1,311 1,338 1,328 1,337 1,271 1,283 93 42 
20171,140 1,237 1,284 1,331 1,296 1,331 1,296 151 43 
20181,236 1,286 1,346 1,389 1,345 1,323 202 44 
20191,307 1,373 1,395 1,382 1,336 311 42 
20201,684 1,606 1,523 1,535 765 35 
20211,619 1,668 1,691 987 36 
20221,760 1,808 1,217 36 
20231,908 1,606 32 
Total$14,455 
Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
(in millions of U.S. dollars)Unaudited
Accident Year2014201520162017201820192020202120222023
2014$105 $275 $444 $571 $681 $761 $823 $865 $894 $934 
201580 267 465 637 753 830 906 938 969 
2016120 306 505 648 766 857 979 1,003 
201791 299 499 653 812 940 995 
2018105 312 470 608 727 881 
2019118 316 444 648 729 
2020102 273 429 530 
2021111 271 434 
202283 284 
202379 
Total$6,838 
Net Liabilities for Loss and Allocated Loss Adjustment Expenses
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$540 
Accident years 2014 - 2023 from tables above
7,617 
All Accident years$8,157 
Overseas General Insurance — Casualty — Long-tail (continued)
Supplementary Information: (Favorable)/ Adverse Prior Period Development
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$(22)
Accident years 2014 - 2023 from tables above
(26)
All Accident years$(48)
Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2023 (Unaudited)
Age in Years1 2 3 4 5 6 7 8 9 10 
Percentage7 %13 %13 %11 %9 %9 %6 %3 %3 %4 %
Overseas General Insurance — Non-Casualty — Short-tail
This product line is comprised of commercial fire, marine (predominantly cargo), surety, personal automobile (in Latin America, Asia Pacific and Japan), personal cell phones, personal residential (including high net worth), energy, and construction. In general, these lines have relatively stable payment and reporting patterns although they are impacted by natural catastrophes mainly in the 2017, 2018, and 2022 accident years. For the Chubb Overseas General non-casualty book, Europe, exclusive of Lloyd's market, makes up about one third, Latin America makes up about one quarter, and Asia makes up about one fifth.
Net Incurred Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
As of December 31 2023
(in millions of U.S. dollars)UnauditedNet IBNR Reserves
Reported Claims (in thousands)
Accident Year2014201520162017201820192020202120222023
2014$1,764 $1,828 $1,775 $1,763 $1,729 $1,719 $1,712 $1,706 $1,698 $1,693 $3 533 
20151,855 1,973 1,947 1,916 1,900 1,892 1,874 1,875 1,870 8 556 
20161,959 1,955 1,942 1,921 1,926 1,957 1,955 1,943 29 568 
20172,114 2,157 2,145 2,126 2,151 2,149 2,115 (6)577 
20182,068 2,156 2,119 2,093 2,062 2,051 42 613 
20192,100 2,119 2,059 2,047 2,043 (12)632 
20202,437 2,301 2,171 2,116 87 534 
20212,524 2,437 2,322 60 542 
20222,800 2,777 168 614 
20232,995 901 594 
Total$21,925 
Overseas General Insurance — Non-Casualty — Short-tail (continued)
Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
(in millions of U.S. dollars)Unaudited
Accident Year2014201520162017201820192020202120222023
2014$721 $1,359 $1,560 $1,619 $1,649 $1,662 $1,677 $1,684 $1,678 $1,680 
2015812 1,469 1,691 1,769 1,790 1,819 1,836 1,839 1,839 
2016966 1,592 1,779 1,847 1,872 1,881 1,887 1,890 
20171,010 1,772 1,940 2,013 2,055 2,114 2,091 
2018960 1,664 1,858 1,924 1,940 1,950 
20191,019 1,674 1,861 1,926 1,959 
20201,036 1,646 1,792 1,908 
2021982 1,750 2,025 
20221,168 2,088 
20231,119 
Total$18,549 
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$139 
Accident years 2014 - 2023 from tables above
3,376 
All Accident years$3,515 
Supplementary Information: (Favorable)/ Adverse Prior Period Development
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$(4)
Accident years 2014 - 2023 from tables above
(264)
All Accident years$(268)
Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2023 (Unaudited)
Age in Years1 2 3 4 5 6 7 8 9 10 
Percentage45 %33 %10 %4 %1 %1 %— %— %— %— %

Global Reinsurance
Chubb analyzes its Global Reinsurance business on a treaty year basis rather than on an accident year basis. Treaty year data was converted to an accident year basis for the purposes of this disclosure. Mix shifts are an important consideration in these product line groupings. As proportional business and excess of loss business have different earning and loss reporting and payment patterns, this change in mix will affect the cash flow patterns across the accident years. In addition, the shift from excess to proportional business over time will make the cash flow patterns of older and more recent years difficult to compare. In general, the proportional business will pay out more quickly than the excess of loss business, as such, using older years development patterns may overstate the ultimate loss estimates in more recent years.

Global Reinsurance — Casualty — Long-tail
This product line includes proportional and excess coverages in general, automobile liability, professional liability, medical malpractice, and workers' compensation, with exposures located around the world. In general, reinsurance exhibits less stable development patterns than primary business. In particular, general casualty reinsurance and excess coverages are long-tailed and can be very volatile.
Global Reinsurance — Casualty — Long-tail (continued)
Net Incurred Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
As of December 31
 2023
(in millions of U.S. dollars)UnauditedNet
IBNR
Reserves
Accident Year2014201520162017201820192020202120222023
2014$330 $331 $336 $339 $340 $344 $327 $327 $326 $326 $6 
2015281 286 296 297 305 301 305 308 307 9 
2016219 223 231 230 239 239 244 250 11 
2017209 211 216 213 214 214 221 6 
2018239 242 249 245 248 255 9 
2019233 242 237 236 233 20 
2020242 246 237 237 42 
2021278 282 286 105 
2022294 296 155 
2023274 211 
Total$2,685 
Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses
Years Ended December 31
(in millions of U.S. dollars)Unaudited
Accident Year2014201520162017201820192020202120222023
2014$91 $183 $216 $247 $263 $274 $284 $293 $298 $304 
201589 158 190 215 230 247 264 273 281 
201657 112 141 157 173 190 206 217 
201746 99 120 138 153 173 185 
201840 94 123 146 168 194 
201939 89 115 138 161 
202041 98 123 147 
202135 86 119 
202239 86 
202330 
Total$1,724 
Net Liabilities for Loss and Allocated Loss Adjustment Expenses
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$279 
Accident years 2014 - 2023 from tables above
961 
All Accident years$1,240 
Supplementary Information: (Favorable)/ Adverse Prior Period Development
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$(16)
Accident years 2014 - 2023 from tables above
22 
All Accident years$6 
Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2023 (Unaudited)
Age in Years1 2 3 4 5 6 7 8 9 10 
Percentage19 %22 %11 %9 %7 %7 %5 %3 %2 %2 %
Global Reinsurance — Non-Casualty — Short-tail
This product line includes property, property catastrophe, marine, credit/surety, mortgage, A&H and energy. This product line is impacted by natural catastrophes, particularly in the 2017, 2018, 2020, 2021, and 2022 accident years. Of the non-catastrophe book, the mixture of business varies by year with approximately 87 percent of loss on proportional treaties in treaty year 2014 and after. This percentage has increased over time with the proportion being approximately 77 percent for treaty years 2014-2017 growing to an average of 93 percent for treaty years 2018 to 2023, with the remainder being written on an excess of loss basis.
Net Incurred Loss and Allocated Loss Adjustment Expenses
As of December 31
 2023
Years Ended December 31
(in millions of U.S. dollars)UnauditedNet
IBNR
Reserves
Accident Year2014201520162017201820192020202120222023
2014$158 $174 $173 $176 $174 $173 $172 $170 $169 $169 $1 
2015144 152 158 158 151 156 154 154 154 1 
2016177 182 185 187 184 181 181 181 1 
2017395 421 451 449 453 455 454 7 
2018278 286 288 284 289 282 2 
2019130 129 125 120 116 3 
2020209 253 277 279 22 
2021340 351 354 23 
2022346 311 69 
2023181 109 
Total$2,481 
Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses

Years Ended December 31
(in millions of U.S. dollars)Unaudited
Accident Year2014201520162017201820192020202120222023
2014$63 $124 $146 $156 $161 $163 $165 $165 $166 $166 
201556 102 130 140 144 148 150 150 151 
201656 129 156 166 172 175 176 177 
2017191 321 400 413 426 433 439 
201894 248 264 267 272 274 
201935 80 94 102 104 
202062 177 215 232 
2021158 277 307 
202274 195 
202336 
Total$2,081 
Net Liabilities for Loss and Allocated Loss Adjustment Expenses
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$11 
Accident years 2014 - 2023 from tables above
400 
All Accident years$411 
Supplementary Information: (Favorable)/ Adverse Prior Period Development
(in millions of U.S. dollars)December 31, 2023
Accident years prior to 2014$— 
Accident years 2014 - 2023 from tables above
(42)
All Accident years$(42)
Global Reinsurance — Non-Casualty — Short-tail (continued)
Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2023 (Unaudited)
Age in Years1 2 3 4 5 6 7 8 9 10 
Percentage33 %40 %14 %5 %3 %2 %1 %— %— %— %

Prior Period Development — Supplementary Information

The following table presents a reconciliation of the loss development triangles above to prior period development:
Components of PPD
Year Ended December 31, 2023 (in millions of U.S. dollars)
(favorable)/unfavorable		2014 - 2022 accident years (implied PPD per loss triangles)Accident years prior to 2014
Other (1)
PPD on loss reserves RIPs, Expense adjustments, and earned premiumsTotal
North America Commercial P&C Insurance
Long-tail$83 $(72)$(187)$(176)$90 $(86)
Short-tail(377)(4)(35)(416)8 (408)
(294)(76)(222)(2)(592)98 (3)(494)
North America Personal P&C Insurance (Short-tail)(131)3 (4)(132)(2)(134)
Overseas General Insurance
Long-tail(26)(22)(2)(50)— (50)
Short-tail(264)(4)(58)(326)— (326)
(290)(26)(60)(4)(376)— (376)
Global Reinsurance
Long-tail22 (16)1 7 — 7 
Short-tail(42)— — (42)7 (35)
(20)(16)1 (35)7 (28)
Subtotal$(735)$(115)$(285)$(1,135)$103 $(1,032)
North America Agricultural Insurance (Short-tail)$(24)$6 $(18)
Corporate (Long-tail)277 — 277 
Consolidated PPD$(882)$109 $(773)
(1)        Other includes the impact of foreign exchange.
(2)     Includes favorable development of $88 million related to our Alternative Risk Solutions business (U.S. and Bermuda) and an adjustment to exclude $92 million in unfavorable development in the workers' compensation line, associated with an increase in exposure for which additional premiums were collected; the remaining difference relates to a number of other items, none of which are individually material.
(3)     Includes premium returns associated with our Alternative Risk Solutions business, which is excluded from the triangles.
(4)     Includes favorable development of $56 million related to International A&H business; the remaining difference relates to a number of other items, none of which are individually material.
Prior Period Development
Prior period development (PPD) arises from changes to loss estimates recognized in the current year that relate to loss events that occurred in previous calendar years and excludes the effect of losses from the development of earned premium from previous accident years. Long-tail lines include lines such as workers' compensation, general liability, and financial lines; while short-tail lines include lines such as most property lines, energy, personal accident, and agriculture. The following table summarizes (favorable) and adverse PPD by segment:
Years Ended December 31
(in millions of U.S. dollars, except for percentages)		Long-tailShort-tailTotal
% of beginning net unpaid reserves (1)
2023
North America Commercial P&C Insurance$(86)$(408)$(494)0.8 %
North America Personal P&C Insurance— (134)(134)0.2 %
North America Agricultural Insurance— (18)(18)— %
Overseas General Insurance(50)(326)(376)0.6 %
Global Reinsurance7 (35)(28)— %
Corporate277 — 277 0.5 %
Total$148 $(921)$(773)1.3 %
2022
North America Commercial P&C Insurance$(229)$(333)$(562)1.0 %
North America Personal P&C Insurance— (186)(186)0.3 %
North America Agricultural Insurance— (61)(61)0.1 %
Overseas General Insurance(65)(383)(448)0.8 %
Global Reinsurance(7)29 22 — %
Corporate359 — 359 0.6 %
Total$58 $(934)$(876)1.6 %
2021
North America Commercial P&C Insurance$(482)$(280)$(762)1.4 %
North America Personal P&C Insurance— (305)(305)0.6 %
North America Agricultural Insurance— 10 10 — %
Overseas General Insurance(106)(335)(441)0.8 %
Global Reinsurance(25)28 3 — %
Corporate 569 — 569 1.1 %
Total$(44)$(882)$(926)1.8 %
(1)     Calculated based on the beginning of period consolidated net unpaid losses and loss expenses.

Significant prior period movements by segment, principally driven by reserve reviews completed during each respective period, are discussed in more detail below. The remaining net development for long-tail lines and short-tail business for each segment and Corporate comprises numerous favorable and adverse movements across a number of lines and accident years, none of which is significant individually or in the aggregate.

North America Commercial P&C Insurance.
Net favorable development in 2023 included $387 million in workers' compensation lines, $248 million in commercial property and marine lines, and $101 million in surety, all mainly driven by lower than expected loss emergence. The favorable development was partially offset by adverse development of $193 million in commercial excess and umbrella lines and $129 million in commercial auto liability, both driven by higher than expected loss emergence.

Net favorable development in 2022 included $496 million in workers' compensation from lower than expected loss emergence, updates to loss development factors, and our annual assessment of multi-claimant events, including industrial accidents. The favorable development was partially offset by net adverse development of $177 million in commercial auto liability, driven by adverse reported loss experience and explicit recognition of anticipated increases in claim severity trend, $96 million from commercial umbrella/excess portfolios, driven by higher than expected loss emergence and increases in our claims severity trend assumptions, and $82 million from medical risk where reported loss activity was higher than expected, driven by claim severity
increases and large loss activity. Net favorable development on our short-tail businesses primarily included $206 million from property and marine portfolios, where paid and reported loss activity for the most recent accident years was lower than expected.

Net favorable development of $762 million in 2021 represented 1.4 percent of the beginning consolidated net unpaid losses and loss expense reserves.

North America Personal P&C Insurance.
Net favorable development in 2023 included $244 million in homeowners and valuables lines, mainly due to lower than expected loss emergence in accident year 2022, partially offset by net adverse development on reported losses of $145 million in personal excess liability in recent accident years.

Net favorable development in 2022 primarily included favorable development in the homeowners and valuables lines of business, driven by lower than expected claims reserve development.

Net favorable development of $305 million in 2021 represented 0.6 percent of the beginning consolidated net unpaid losses and loss expense reserves.

Overseas General Insurance.
Net favorable development in 2023 included $253 million in property and marine lines, mainly in accident years 2020 through 2022, driven by favorable loss development across all regions, favorable catastrophe development in recent accident years, and specific case reductions. Net favorable development also included $77 million in professional lines, including cyber, driven by favorable loss development in the U.K. and Europe regions.

Net favorable development in 2022 included $105 million in A&H lines, driven by favorable loss development in the Asia Pacific, U.K., and Europe regions. Net favorable development also included $100 million in property lines, driven by favorable loss development across most regions, favorable catastrophe development in recent accident years, specific case reductions, and salvage and subrogation recoveries.

Net favorable development of $441 million in 2021 represented 0.8 percent of the beginning consolidated net unpaid losses and loss expense reserves.

Corporate.
Net adverse development in 2023, 2022, and 2021, included adverse development for asbestos claims of $99 million, $61 million, and $52 million, respectively, and molestation claims of $49 million, $155 million, and $417 million, respectively. The $417 million adverse development in 2021 was primarily driven by a settlement-in-principle with the BSA regarding molestation claims. Refer to the Molestation claims section below for further information. Net adverse development for all years also included adverse development for environmental liabilities and other exposures.

Molestation claims
Chubb's exposure to molestation claims principally arises out of liabilities acquired when it purchased CIGNA's P&C business in 1999, and Chubb Corp in 2016. The vast majority of the current liability relates to exposure from "reviver" legislation in certain states that allow civil claims relating to molestation to be asserted against policyholders that would otherwise be barred by statutes of limitations. These exposures are predominantly included in our inactive run-off operations included in Corporate with an immaterial amount in the North America Commercial P&C segment.

In December 2021, Chubb reached an agreement-in-principle regarding the bankruptcy of the Boy Scouts of America (BSA). Under this agreement, which remains contingent upon final court approval on appeal, our inactive run-off company, Century Indemnity Company, and certain active Chubb companies obtained a broad release for all Chubb companies from BSA-related abuse claims for $800 million. This agreement was approved by the bankruptcy court in the third quarter of 2022. In the first quarter of 2023, the District Court issued an order approving the Boy Scouts of America (BSA) bankruptcy plan in full. We paid $800 million per the agreement, with $300 million paid in 2022, and the remaining $500 million paid in 2023.
Asbestos and environmental (A&E)
Chubb's exposure to A&E claims principally arises out of liabilities acquired when it purchased Westchester Specialty in 1998, CIGNA's P&C business in 1999, and Chubb Corp in 2016. The following table presents a roll-forward of consolidated A&E loss reserves including allocated loss expense reserves for A&E exposures, and the valuation allowance for uncollectible paid and unpaid reinsurance recoverables:
AsbestosEnvironmentalTotal
(in millions of U.S. dollars)GrossNetGrossNetGrossNet
Balance at December 31, 2020$1,351 $873 $517 $379 $1,868 $1,252 
Incurred activity96 64 52 40 148 104 (1)
Paid activity(221)(137)(167)(117)(388)(254)
Balance at December 31, 20211,226 800 402 302 1,628 1,102 
Incurred activity87 55 125 77 212 132 (1)
Paid activity(215)(152)(115)(69)(330)(221)
Balance at December 31, 20221,098 703 412 310 1,510 1,013 
Incurred activity180 120 88 63 268 183 (1)
Paid activity(258)(169)(105)(82)(363)(251)
Balance at December 31, 2023$1,020 $654 $395 $291 $1,415 $945 
(1)    Excludes unallocated loss expenses and the net activity reflects third-party reinsurance other than the aggregate excess of loss reinsurance provided by National Indemnity Company (NICO) to Westchester Specialty (see Westchester Specialty section below).

The A&E net loss reserves including allocated loss expense reserves and valuation allowance for uncollectible reinsurance at December 31, 2023 and 2022, shown in the table above is comprised of:
December 31
(in millions of U.S. dollars)20232022
Brandywine operations$570 $602 
Westchester Specialty89 98 
Chubb Corp241 266 
Other, mainly Overseas General Insurance45 47 
Total$945 $1,013 

Brandywine Run-off entities – The Restructuring Plan and uncertainties relating to Chubb's ultimate Brandywine exposure

In 1996, the Pennsylvania Insurance Commissioner approved a plan to restructure INA Financial Corporation and its subsidiaries (the Restructuring) which included the division of Insurance Company of North America (INA) into two separate corporations:

(1) An active insurance company that retained the INA name and continued to write P&C business; and
(2) An inactive run-off company, now called Century Indemnity Company (Century).

As a result of the division, predominantly all A&E and certain other liabilities of INA were ascribed to Century and extinguished, as a matter of Pennsylvania law, as liabilities of INA.

As part of the Restructuring, most A&E liabilities of various U.S. affiliates of INA were reinsured to Century. Century and certain other run-off companies having A&E and other liabilities were contributed to Brandywine Holdings.

The U.S.-based Chubb INA companies assumed two contractual obligations in respect of the Brandywine operations in connection with the Restructuring: a surplus maintenance obligation in the form of the excess of loss (XOL) agreement and a dividend retention fund obligation.
XOL Agreement
In 1996, in connection with the Restructuring, a Chubb INA insurance subsidiary provided reinsurance coverage to Century in the amount of $800 million under an Aggregate Excess of Loss Reinsurance Agreement (XOL Agreement), triggerable if the statutory capital and surplus of Century falls below $25 million or if Century lacks liquid assets with which to pay claims as they become due.

Dividend Retention Fund
INA Financial Corporation established and funded a dividend retention fund (the Dividend Retention Fund) consisting of $50 million plus investment earnings. The full balance of the Dividend Retention Fund was contributed to Century as of December 31, 2002. Under the Restructuring Order, while any obligation to maintain the Dividend Retention Fund is in effect, to the extent dividends are paid by INA Holdings Corporation to its parent, INA Financial Corporation, and to the extent INA Financial Corporation then pays such dividends to INA Corporation, a portion of those dividends must be withheld to replenish the principal of the Dividend Retention Fund to $50 million. In 2023 and 2022, $75 million was withheld from such dividends and deposited into the Dividend Retention Fund as a result of dividends paid up to the INA Corporation. Pursuant to a 2011 amendment to the Restructuring Order, capital contributions from the Dividend Retention Fund to Century are not required until the XOL Agreement has less than $200 million of capacity remaining on an incurred basis for statutory reporting purposes. The amount of the required capital contribution shall be the lesser of the amount necessary to restore the XOL Agreement remaining capacity to $200 million or the Dividend Retention Fund balance. In 2023 and 2022, capital contributions of $75 million and $106 million were made, respectively, from the Dividend Retention Fund to Century. The Dividend Retention Fund may not be terminated without prior written approval from the Pennsylvania Insurance Commissioner.

In 2004, Chubb INA contributed $100 million to Century in exchange for a surplus note. After giving effect to the surplus note, contributions from the Dividend Retention Fund, results from operations and other items impacting statutory surplus, the statutory surplus of Century at December 31, 2023, was $25 million and $712 million in statutory-basis losses have been ceded to the XOL Agreement on an inception-to-date basis. The XOL Agreement statutory-basis remaining limit at December 31, 2023, is $88 million. Century reports the amount ceded under the XOL Agreement in accordance with statutory accounting principles, which differ from U.S. GAAP by, among other things, allowing Century to discount its liabilities, including certain asbestos related and environmental pollution liabilities and Century's reinsurance payable to active companies. For U.S. GAAP reporting purposes, intercompany reinsurance recoverables related to the XOL are eliminated upon consolidation.

While Chubb believes it has no legal obligation to fund Century losses above the XOL limit of coverage, Chubb's consolidated results would nevertheless continue to include any losses above the limit of coverage for so long as the Brandywine companies remain consolidated subsidiaries of Chubb.

Certain active Chubb companies are primarily liable for asbestos, environmental, and other exposures that they have reinsured to Century. Accordingly, if Century were to become insolvent and placed into rehabilitation or liquidation, some or all of the recoverables due to these active Chubb companies from Century could become uncollectible. At December 31, 2023 and 2022, the aggregate reinsurance recoverables owed by Century to certain active Chubb companies were approximately $1.8 billion and $1.9 billion, respectively, on an undiscounted basis. Chubb believes the active company intercompany reinsurance recoverables, which relate to direct liabilities payable over many years, are not impaired. At December 31, 2023 and 2022, Century's carried gross reserves (including reserves assumed from the active Chubb companies) were $1.7 billion and $2.1 billion, respectively. Changes in laws and regulations may have an adverse effect on Century's reserves; for example, the enactment of "reviver" statutes relating to claims of sexual molestation may give rise to additional claims that would have been barred by the statutes of limitations in effect at the time of the alleged molestation. Should Century's loss reserves experience adverse development, as a result of such changes or otherwise, in the future and should Century be placed into rehabilitation or liquidation, the reinsurance recoverables due from Century to certain active Chubb companies would be payable only after the payment in full of certain expenses and liabilities, including administrative expenses and direct policy liabilities. Thus, the intercompany reinsurance recoverables would be at risk to the extent of the shortage of assets remaining to pay these recoverables.

Westchester Specialty – impact of NICO contracts on Chubb’s run-off entities

As part of the Westchester Specialty acquisition in 1998, NICO provided a 75 percent pro-rata share of $1.0 billion of reinsurance protection on losses and loss adjustment expenses incurred on or before December 31, 1996, in excess of a retention of $721 million. At December 31, 2023, the remaining unused incurred limit under the Westchester NICO agreement was $337 million.