We have established and maintain long term incentive plans (LTIP) for the granting of restricted common shares (Restricted stock), PSUs and stock options to our employees. At December 31, 2019, the total number of authorized common stock under the LTIP was 51.5 million shares, of which we have 16.4 million shares available for issuance. Share‑based compensation expense consisted of the following:

	2019		2018		2017
	(In millions)
Restricted stock	$	53	$	40	$	56
Stock options		10		10		9
Performance share units		22		22		21
Share-based compensation expense before income taxes	$	85	$	72	$	86
Income tax benefit on share-based compensation expense	$	—	$	—	$	1

Based on share‑based compensation awards outstanding at December 31, 2019, unearned compensation expense, before income taxes, will be recognized in future years as follows (in millions): 2020: $53, 2021: $29 and 2022: $4.

Restricted stock generally vests equally on an annual basis over a three-year term and are valued based on the prevailing market price of our common stock on the date of grant. The following is a summary of restricted stock award activity in 2019:

		Shares of Restricted Common Stock			Weighted - Average Price on Date of Grant
	(In thousands, except per share amounts)
Outstanding at January 1, 2019			2,881		$	48.70
Granted			965			56.87
Vested (a)			(1,742	)		47.35
Forfeited			(90	)		52.67
Outstanding at December 31, 2019			2,014		$	53.61

PSUs generally vest three years from the date of grant and are valued using a Monte Carlo simulation on the date of grant. The number of shares of common stock to be issued under a PSU agreement is based on a comparison of the Corporation’s total shareholder return (TSR) to the TSR of a predetermined group of peer companies over a three‑year performance period ending December 31 of the year prior to settlement of the grant. Payouts of the performance share awards will range from 0% to 200% of the target awards based on the Corporation’s TSR ranking within the peer group. Dividend equivalents for the performance period will accrue on performance shares but will only be paid out on earned shares after the performance period. The following is a summary of PSU activity in 2019:

	Performance Share Units			Weighted - Average Fair Value on Date of Grant
	(In thousands, except per share amounts)
Outstanding at January 1, 2019		1,063		$	53.98
Granted		269			68.87
Vested (a)		(391	)		51.00
Forfeited		(12	)		52.05
Outstanding at December 31, 2019		929		$	59.57

The following weighted average assumptions were utilized to estimate the fair value of PSU awards:

	2019			2018			2017
Risk free interest rate		2.48	%		2.39	%		1.55	%
Stock price volatility		0.369			0.400			0.387
Contractual term in years		3.0			3.0			3.0
Grant date price of Hess common stock	$	56.74		$	48.48		$	51.03

Stock options vest over three years from the date of grant, have a 10‑year term, and the exercise price equals the market price of our common stock on the date of grant. The following is a summary of stock options activity in 2019:

	Number of options (In thousands)			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term
Outstanding at January 1, 2019		5,170		$	61.91	4.3 years
Granted		527			56.74
Exercised		(744	)		54.23
Forfeited		(652	)		57.69
Outstanding at December 31, 2019		4,301		$	63.24	4.8 years

At December 31, 2019, there were 4.3 million outstanding stock options (3.1 million exercisable) with a weighted average remaining contractual life of 4.8 years (3.4 years for exercisable options) and an aggregated intrinsic value of $39 million ($22 million for exercisable options).

The following weighted average assumptions were utilized to estimate the fair value of stock options:

	2019			2018			2017
Risk free interest rate		2.55	%		2.74	%		2.17	%
Stock price volatility		0.359			0.322		0.333
Dividend yield		1.76	%		2.06	%		1.96	%
Expected life in years		6.0			6.0			6.0
Weighted average fair value per option granted	$	18.08		$	13.69		$	14.51

In estimating the fair value of PSUs and stock options, the risk-free interest rate is based on the vesting period of the award and is obtained from published sources. The stock price volatility is determined from the historical stock prices of the Corporation using the expected term.