Units Outstanding – MPLX had 1,058,355,471 common units outstanding as of December 31, 2019. Of that number, 665,997,540 were owned by MPC, which also owns the non-economic GP interest as described below. MPLX had 600,000 Series B preferred units outstanding as of December 31, 2019. The sections below describe activities and events which impacted our unit balances throughout the year.

Merger - In connection with the Merger and as discussed in Note 4, each common unit held by ANDX’s public unitholders was converted into the right to receive 1.135 MPLX common units while ANDX common units held by certain affiliates of MPC were converted into the right to receive 1.0328 MPLX common units. This resulted in the issuance of MPLX common units of approximately 102 million units to public unitholders and approximately 161 million units to MPC in connection with MPLX's acquisition of ANDX on July 30, 2019.

Series A Redeemable Preferred Unit Conversions - During 2019, certain holders of Series A preferred units exercised their rights to convert their Series A preferred units into approximately 1.2 million common units as discussed in Note 9.

GP/IDR Exchange – On February 1, 2018, MPC cancelled its IDRs and converted its economic GP Interest in MPLX LP to a non-economic general partner interest in exchange for 275 million newly issued MPLX LP common units. These units had a fair value of $10.4 billion as of the transaction date as recorded on the Consolidated Statements of Equity. As a result of this transaction, the general partner units and IDRs were eliminated, are no longer outstanding, and no longer participate in distributions of cash from MPLX. MPC continues to own the non-economic GP Interest in MPLX LP. See Note 7 for more information on the net income per unit calculation.

Class B Conversions - On July 1, 2016 and July 1, 2017, each Class B unit of MPLX LP was converted, in two equal installments, into 1.09 MPLX LP common units and the right to receive $6.20 in cash. Upon the conversion of each tranche of the Class B units, the right of the unitholder, M&R MWE Liberty LLC and certain of its affiliates (“M&R”), to vote as a common unitholder of MPLX was limited to a maximum of five percent of MPLX’s outstanding common units. Additionally, M&R was given the right with respect to such converted units to participate in MPLX’s underwritten offerings of our common units including continuous equity or similar programs in an amount up to 20 percent of the total number of common units

offered by MPLX. M&R may freely transfer such converted units, and M&R has the right to demand that MPLX conduct up to three underwritten offerings beginning in 2017, but restricted to no more than one offering in any twelve-month period. Following the July 1, 2017 conversion, all MPLX Class B units were eliminated, are no longer outstanding and no longer participate in distributions of cash from MPLX.

ATM Program – On March 13, 2018, MPLX entered into a Third Amended and Restated Distribution Agreement, providing for the at-the-market issuances of common units having an aggregate offering price of up to approximately $1.7 billion, in amounts, at prices and on terms determined by market conditions and other factors at the time of the offerings (such continuous offering program, or at-the-market program is referred to as the “ATM Program”). During the years ended December 31, 2019 and 2018, MPLX issued no common units under the ATM Program. During the year ended December 31, 2017, MPLX issued an aggregate of 13,846,998 common units under the ATM Program generating net proceeds of approximately $473 million. MPLX used the net proceeds from sales under the ATM Program for general business purposes, including repayment or refinancing of debt, and funding for acquisitions, working capital requirements and capital expenditures.



(In units)	Common	Class B		General Partner⁽¹⁾		Total
Balance at December 31, 2016	357,193,288	3,990,878		7,371,105		368,555,271
Unit-based compensation awards	268,167	—		5,472		273,639
Issuance of units under the ATM Program	13,846,998	—		282,591		14,129,589
Contribution of HST/WHC/MPLXT (See Note 4)	12,960,376	—		264,497		13,224,873
Contribution of the Joint-Interest Acquisition (See Note 4)	18,511,134	—		377,778		18,888,912
Class B Conversion	4,350,057	(3,990,878	)	7,330		366,509
Balance at December 31, 2017	407,130,020	—		8,308,773		415,438,793
Unit-based compensation awards	348,387	—		140		348,527
Contribution of Refining Logistics and Fuels Distribution (See Note 4)	111,611,111	—		2,277,778		113,888,889
Conversion of GP economic interests	275,000,000	—		(10,586,691	)	264,413,309
Balance at December 31, 2018	794,089,518	—		—		794,089,518
Unit-based compensation awards	288,031	—		—		288,031
Issuance of units in connection with the Merger	262,829,592	—		—		262,829,592
Conversion of Series A preferred units	1,148,330	—		—		1,148,330
Balance at December 31, 2019	1,058,355,471	—		—		1,058,355,471

Series B Preferred Units - Prior to the Merger, ANDX issued 600,000 units of 6.875 percent Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units representing limited partner interests of ANDX at a price to the public of $1,000 per unit. Upon completion of the Merger, the ANDX preferred units converted to preferred units of MPLX representing substantially equivalent limited partnership interests in MPLX (the “Series B preferred units”). The Series B preferred units are pari passu with the Series A preferred units with respect to distribution rights and rights upon liquidation. Distributions on the Series B preferred units are payable semi-annually in arrears on the 15th day, or the first business day thereafter, of February and August of each year up to and including February 15, 2023. After February 15,

2023, the holders of Series B preferred units are entitled to receive cumulative, quarterly distributions payable in arrears on the 15th day of February, May, August and November of each year, or the first business day thereafter, based on a floating annual rate equal to the three-month LIBOR plus 4.652 percent.

The changes in the Series B preferred unit balance from the Merger through December 31, 2019 are summarized below and are included in the Consolidated Balance Sheets and Consolidated Statements of Equity within “Equity of Predecessor” for the period prior to the Merger and within “Series B preferred units” for the period following the Merger. The Series B preferred units are recorded at fair value as of July 30, 2019.

TexNew Mex Units - Prior to the Merger, MPC held 80,000 Andeavor Logistics TexNew Mex units, representing all outstanding units. At the time of the Merger, each Andeavor Logistics TexNew Mex unit was automatically converted into TexNew Mex units of MPLX with substantially the same rights and obligations as the Andeavor Logistics TexNew Mex units. The TexNew Mex units represent the right to receive quarterly distribution payments in an amount calculated using the distributable cash flow generated by a particular portion of the TexNew Mex pipeline system, in excess of a base amount and adjusted for previously agreed upon stipulations and contingencies. No distributions were payable to TexNew Mex unitholders for distributable cash flow generated during the post-Merger period in 2018. In 2019, distributions of less than $1 million were earned by the TexNew Mex units, which were declared in January of 2020 and paid in February 2020.

Issuance of Additional Securities – The Partnership Agreement authorizes MPLX to issue an unlimited number of additional securities for the consideration and on the terms and conditions determined by the general partner without the approval of the unitholders.

Net Income Allocation – In preparing the Consolidated Statements of Equity, net income attributable to MPLX LP is allocated to Series A and Series B preferred unitholders first and subsequently allocated to the limited partner unitholders in accordance with their respective ownership percentages. Prior to 2018, when distributions related to the IDRs were made, earnings equal to the amount of those distributions were first allocated to the general partner before the remaining earnings are allocated to the unitholders, based on their respective ownership percentages. The following table presents the allocation of the general partner’s GP Interest in net income attributable to MPLX, for income statement periods occurring prior to the exchange of the GP economic interests:



(In millions)	2017
Net income attributable to MPLX LP	$	794
Less: Preferred unit distributions	65
General partner's IDRs and other	310
Net income attributable to MPLX LP available to general and limited partners	419

General partner's two percent GP Interest in net income attributable to MPLX LP	8
General partner's IDRs and other	310
General partner's GP Interest in net income attributable to MPLX LP	$	318

Cash Distributions – The Partnership Agreement sets forth the calculation to be used to determine the amount and priority of cash distributions that the common unitholders and preferred unitholders will receive. In accordance with the Partnership Agreement, on January 23, 2020, MPLX declared a quarterly cash distribution, based on the results of the fourth quarter of 2019, totaling $715 million, or $0.6875 per common unit. This rate was also received by Series A preferred unitholders. These distributions were paid

on February 14, 2020 to unitholders of record on February 4, 2020. Distributions for the fourth quarter of 2018 were $0.6475 per common unit while distributions for the twelve months ended December 31, 2019 and 2018 were $2.6900 and $2.5300 per common unit, respectively. The $715 million of common unit distributions is net of $12.5 million in quarterly distributions waived by MPC. This waiver was instituted in 2017 under the terms of ANDX’s historical partnership agreement with Andeavor. The waiver is no longer applicable after 2019 based on the original term in the waiver agreement.

Additionally, as a result of the Merger, 600,000 ANDX preferred units were converted into 600,000 Series B preferred units of MPLX. Series B preferred unitholders are entitled to receive, when and if declared by the board, a fixed distribution of $68.75 per unit, per annum, payable semi-annually in arrears on February 15 and August 15, or the first business day thereafter, up to and including February 15, 2023. After February 15, 2023, the holders of Series B preferred units are entitled to receive cumulative, quarterly distributions payable in arrears on the 15th day of February, May, August and November of each year, or the first business day thereafter, based on a floating annual rate equal to the three-month LIBOR plus 4.652 percent. MPLX made a cash distribution to holders of the Series B preferred unitholders on February 15, 2020 for approximately $21 million.

The allocation of total quarterly cash distributions to general, limited, and preferred unitholders is as follows for the years ended December 31, 2019, 2018 and 2017. MPLX’s distributions are declared subsequent to quarter end; therefore, the following table represents total cash distributions applicable to the period in which the distributions were earned.



(In millions)	2019		2018		2017
General partner's distributions:
General partner's distributions on general partner units	$	—	$	—	$	25
General partner's distributions on IDRs⁽¹⁾	—		—		303
Total distribution on general partner units and IDRs	—		—		328
Limited partners' distributions:
Common unitholders, includes common units of general partner	2,635		1,985		895
Series A preferred unit distributions	81		75		65
Series B preferred unit distribution	42		—		—
Total cash distributions declared	$	2,758	$	2,060	$	1,288