The 2015 Stock and Incentive Compensation Plan (the 2015 Stock Plan) and the New Hire Stock and Incentive Plan allow for the issuance of stock options, restricted stock units and awards, and performance stock units. As of January 3, 2021, approximately 3.5 million shares remained available for future grants under the 2015 Stock Plan. There is no set number of shares reserved for issuance under the New Hire Stock and Incentive Plan.

We issue restricted stock units (RSU) and performance stock units (PSU), both of which are considered restricted stock. We grant restricted stock pursuant to the 2015 Stock Plan and satisfy such grants through the issuance of new shares. RSU are share awards that, upon vesting, will deliver to the holder shares of our common stock. RSU generally vest over a four-year period with equal vesting annually. We issue PSU for which the number of shares issuable at the end of a three-year performance period is based on our performance relative to specified earnings per share targets and continued employment through the vesting period.


	Restricted Stock Units (RSU)	Performance Stock Units (PSU)(1)	Weighted-Average Grant- Date Fair Value per Share
Units in thousands			RSU		PSU
Outstanding at December 31, 2017	2,085	542	$	172.92	$	166.15
Awarded	655	336	$	322.04	$	232.08
Vested	(731)	(188)	$	170.50	$	176.15
Cancelled	(169)	(30)	$	172.30	$	162.54
Outstanding at December 30, 2018	1,840	660	$	227.00	$	196.99
Awarded	698	(41)	$	313.70	$	254.52
Vested	(694)	(283)	$	205.51	$	133.11
Cancelled	(144)	(65)	$	225.48	$	181.79
Outstanding at December 29, 2019	1,700	271	$	271.49	$	258.66
Awarded	878	(78)	$	329.83	$	344.22
Vested	(655)	(117)	$	239.19	$	400.74
Cancelled	(202)	(76)	$	273.13	$	266.63
Outstanding at January 3, 2021	1,721	—	$	313.35	—

(1)The number of units reflect the estimated number of shares to be issued at the end of the performance period. Awarded units are presented net of performance adjustments.


In millions	2020		2019		2018
Pre-tax intrinsic value of outstanding restricted stock:

RSU	$	637	$	565	$	549
PSU	$	—	$	90	$	197

Fair value of restricted stock vested:

RSU	$	206	$	210	$	125
PSU	$	47	$	38	$	33


	Options (in thousands)	Weighted- Average Exercise Price
Outstanding at December 31, 2017	322	$	46.93
Exercised	(130)	$	35.68

Outstanding at December 30, 2018	192	$	54.52
Exercised	(134)	$	53.61

Outstanding at December 29, 2019	58	$	56.65
Exercised	(48)	$	56.16

Outstanding and exercisable at January 3, 2021	10	$	59.11

The aggregate intrinsic value of options outstanding and options exercisable as of January 3, 2021 was $3 million. Aggregate intrinsic value represents the product of the number of options outstanding multiplied by the difference between our closing stock price per share on the last trading day of the fiscal period, which was $370.00 as of December 31, 2020, and the exercise price. Total intrinsic value of options exercised was $14 million, $34 million, and $33 million in 2020, 2019, and 2018, respectively.

A total of 15.5 million shares of our common stock have been reserved for issuance under our 2000 Employee Stock Purchase Plan, or ESPP. The ESPP permits eligible employees to purchase common stock at a discount through payroll deductions during defined offering periods. The price at which stock is purchased under the ESPP is equal to 85% of the fair market value of the common stock on the first day of the offering period or purchase date, whichever is lower. The initial offering period commenced in July 2000.

Approximately 0.2 million, 0.2 million, and 0.3 million shares were issued under the ESPP during 2020, 2019, and 2018, respectively. As of January 3, 2021 and December 29, 2019, there were approximately 13.3 million and 13.5 million shares available for issuance under the ESPP, respectively.

During 2020, 2019, and 2018, we repurchased approximately 2.3 million shares for $735 million, 1.1 million shares for $324 million, and 0.6 million shares for $201 million (of which 0.3 million shares for $103 million was repurchased concurrently with the offering of our 2023 Notes), respectively. As of January 3, 2021, authorizations to repurchase $15 million of our common stock remained available under the $750 million share repurchase program authorized by our Board of Directors on February 5, 2020. The repurchases may be completed under a 10b5-1 plan or at management’s discretion.


In millions	2020		2019		2018
Cost of product revenue	$	21	$	19	$	16
Cost of service and other revenue	4		4		3
Research and development	74		66		60
Selling, general and administrative	95		105		114
Share-based compensation expense, before taxes	194		194		193
Related income tax benefits	(43)		(41)		(39)
Share-based compensation expense, net of taxes	$	151	$	153	$	154

In August 2020, we modified the performance period for our performance stock units granted in 2018, which vested at the end of the three-year period ended January 3, 2021. This modification affected 49 employees and resulted in total incremental share-based compensation cost of approximately $47 million in 2020. In February 2021, we modified the metrics and reduced the maximum potential payouts for our performance stock units granted in 2019 and 2020, which vest at the end of the three-year periods ended January 2, 2022 and January 1, 2023, respectively.

The assumptions used for the specified reporting periods and the resulting estimates of weighted-average fair value per share for stock purchased under the ESPP were as follows:


	2020		2019		2018
Risk-free interest rate	0.11% - 2.04%		1.88% - 2.56%		1.22% - 2.45%
Expected volatility	30% - 45%		30% - 38%		29% - 39%
Expected term	0.5 - 1.0 year		0.5 - 1.0 year		0.5 - 1.0 year
Expected dividends	0%		0%		0%
Weighted-average grant-date fair value per share	$	75.57	$	75.47	$	61.59

As of January 3, 2021, approximately $496 million of total unrecognized compensation cost related to restricted stock and ESPP shares issued to date was expected to be recognized over a weighted-average period of approximately 2.8 years.