The P. H. Glatfelter Amended and Restated Long Term Incentive Plan (the “LTIP”) provides for the issuance of Glatfelter common stock to eligible participants in the form of restricted stock units, restricted stock awards, non-qualified stock options, performance shares, incentive stock options and performance units. As of December 31, 2018, there were 1,990,742 shares of common stock available for future issuance under the LTIP.

Pursuant to the terms of the LTIP, we have issued to eligible participants restricted stock units, performance share awards and stock only stock appreciation rights (“SOSARs”).

Restricted Stock Units (“RSUs”) and Performance Share Awards (“PSAs”)Awards of RSUs and PSAs are made under our LTIP. The vesting of RSUs is generally based on the passage of time, generally over a three -year period or in certain instances the RSUs were issued with fiver year cliff vesting. PSAs are issued to members of management and vesting is based on achievement of cumulative financial performance targets covering a two year period followed by an additional one-year service period. The performance measures include a minimum, target and maximum performance level providing the grantees an opportunity to receive more or less shares than targeted depending on actual financial performance. In addition, beginning in 2018, PSA awards include a modifier based on the three-year total shareholder return relative to a broad market index. For RSUs the grant date fair value of the awards, or the closing price per common share on the date of the award, is used to determine the amount of expense to be recognized over the applicable service period. For PSAs, the grant date fair value is estimated using a lattice model. The significant inputs include the stock price, volatility, dividend yield, and risk-free rate of return. Settlement of RSUs and PSAs will be made in shares of our common stock currently held in treasury.

The following table summarizes RSU and PSA activity during the past three years:

The amount granted in 2018, 2017 and 2016 includes 184,834, 163,274 and 199,693 PSAs, respectively, exclusive of reinvested dividends. The weighted average grant date fair value per unit for awards in 2018, 2017 and 2016 was $20.20, $22.32 and $18.08, respectively. As of December 31, 2018, unrecognized compensation expense for outstanding RSUs and PSAs totaled $5.2 million. The weighted average remaining period over which the expense will be recognized is 1.3 years.

	2018					2017					2016
SOSARS	Shares			Wtd Avg Exercise Price		Shares			Wtd Avg Exercise Price		Shares			Wtd Avg Exercise Price
Outstanding at January 1,		2,561,846		$	17.87		2,736,616		$	17.64		2,199,742		$	17.82
Granted		—			—		—			—		743,925		17.54
Exercised		(158,545	)		13.31		(157,140	)		13.76		(61,190	)		10.70
Canceled / forfeited		(68,559	)		21.09		(17,630	)		18.46		(145,861	)		22.80
Outstanding at December 31,		2,334,742		$	18.08		2,561,846		$	17.87		2,736,616		$	17.64
Exercisable at December 31,		2,134,297			18.13		2,011,075		17.56			1,740,591			16.19
Vested and expected to vest		2,334,742					2,561,846					2,725,611

SOSAR Grants
Weighted average grant date fair value per share		—					—				$	4.07
Aggregate grant date fair value (in thousands)		—					—				$	3,013
Black-Scholes assumptions
Dividend yield		—					—					2.85	%
Risk free rate of return		—					—					1.34	%
Volatility		—					—					31.97	%
Expected life		—					—				6
Compensation expense (in thousands)	$	317				$	1,266				$	2,607

Under terms of the SOSAR, the recipients receive the right to receive a payment in the form of shares of common stock equal to the difference, if any, in the fair market value of one share of common stock at the time of exercising the SOSAR and the exercise price. The SOSARs vest ratably over a three year period. No SOSARs were issued during 2018 or 2017. As of December 31, 2018, the intrinsic value of SOSARs vested and expected to vest totaled $0 million and the remaining weighted average contractual life of outstanding SOSARs was 4.7 years.