Incentive Based Compensation Plans (Tables)

The weighted average grant date fair value of these awards was based on the following weighted average Black-Scholes assumptions:



	2018		2017		2016
Exercise price per share	$14.52		$15.80		$7.22
Expected annual dividend yield	1.4	%	1.3	%	2.8	%
Expected life in years	6.45		6.4		6.3
Expected volatility	43	%	42	%	36	%
Risk-free interest rate	2.8	%	2.1	%	1.4	%
Weighted average grant date fair value of stock option awards granted	$5.83		$6.07		$1.97

The following is a summary of stock option award activity in 2018.



	Number	Weighted Average	Weighted Average Remaining	Aggregate Intrinsic Value
	of Shares	Exercise Price	Contractual Term	(in millions)
Outstanding at beginning of year	10,330,776	$25.52
Granted	856,890	$14.52
Exercised	(1,878,836)	$14.02
Canceled	(3,128,823)	$31.64
Outstanding at end of year	6,180,007	$24.39	5 years	$	4
Exercisable at end of year	4,523,008	$28.46	3 years	$	1
Expected to vest	1,635,216	$13.25	8 years	$	3

The following is a summary of restricted stock and restricted stock unit award activity in 2018.



	Awards		Weighted Average Grant Date Fair Value
Unvested at beginning of year	7,572,845		$14.24
Granted	4,817,577		$14.82
Vested and Exercised	(3,003,321	)	$15.79
Canceled	(882,155	)	$14.06
Unvested at end of year	8,504,946		$14.04

The key assumptions used in the Monte Carlo simulation to determine the fair value of stock-based performance units granted in 2018, 2017 and 2016 were:



	2018		2017		2016
Valuation date stock price	$14.17		$14.17		$14.17
Expected annual dividend yield	1.4	%	1.4	%	1.4	%
Expected volatility	39	%	43	%	52	%
Risk-free interest rate	2.5	%	2.6	%	2.4	%
Fair value of stock-based performance units outstanding	$19.60		$19.45		$21.51