Stock Incentive Plans

We grant to certain employees RSUs, RSAs, PSUs and stock options (collectively, stock incentive awards) under our 2016 Equity Incentive Plan and 2017 Long-Term Incentive Plan (LTIP) and prior to the 2017 LTIP, under our 2014 and 2009 LTIPs. The 2017 LTIP was approved by stockholders in June 2017 and replaced the 2014 LTIP. Shares awarded under the plans are subject to forfeiture if the participant leaves the company for reasons other than those permitted under the plans such as retirement, death or disability.

RSU awards granted either cliff vest or ratably vest generally over a three-year service period, as defined in the terms of each award. PSU awards vest at the end of a three-year performance period, based on performance criteria determined by the Executive Compensation Committee of the Board of Directors at the time of award. The number of shares earned may equal, exceed or be less than the targeted number of shares depending on whether the performance criteria are met, surpassed or not met. Stock options expire 10 years from the grant date. Our performance-based stock options vest ratably over 55 months based on the performance of our common stock relative to that of a specified peer group. Our service-based stock options vest ratably over 19 months to three years.

In connection with our acquisition described in Note 10, RSAs and PSUs were granted. The RSAs vest ratably, generally over a three-year service period. The PSUs are contingent upon achievement of specific technology and commercialization milestones.

Stock Incentive Awards



	Stock Incentive Awards(a)
	Shares		Weighted-Average Grant Date Fair Value		Weighted-Average Remaining Contractual Term in Years
Units outstanding at January 1, 2017	55.1		$	19.77	2.5
Granted	16.7		$	26.75
Settled	(16.3	)	$	24.65
Forfeited or expired	(2.6	)	$	26.67
Units outstanding at December 31, 2017	52.9		$	21.75	2.0

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(a)	Includes the target amount of PSUs.

Our weighted-average assumptions used to value our stock options are a dividend yield of 4.43% and 4.60%, expected volatility of 25.0% and 26.1%, a risk-free interest rate of 1.97% and 2.00%, and an expected option life of 5.84 and 6.59 years for options issued during the years ended December 31, 2017 and 2015. There were no stock options issued during the year ended December 31, 2016.

Total compensation expense related to the above awards was $585 million, $627 million and $422 million in the years ended December 31, 2017, 2016 and 2015.

At December 31, 2017 the total unrecognized compensation expense for nonvested equity awards granted was $278 million. This expense is expected to be recorded over a weighted-average period of 1.7 years. The total fair value of stock incentive awards vested was $421 million, $325 million and $228 million in the years ended December 31, 2017, 2016 and 2015.