The Company’s Amended and Restated 2017 Incentive Stock Plan (the “2017 Plan”) authorizes the Compensation Committee of the Board of Directors to issue up to 5,126,950 shares of various stock awards including stock options, performance-based restricted stock units, restricted stock units and other forms of equity-based awards to key employees and directors. Options granted and outstanding vest over the requisite service period and expire ten years from the date of grant.

Year	Options		Exercise Price
2018		255,072	$	21.30
2017		397,759	$	14.30
2016		271,350	$	11.62

Options exercised in 2018, 2017 and 2016 were as follows:

Year	Options		Exercise Price
2018		191,169	$9.97 to $20.93
2017		375,292	$9.97 to $20.93
2016		334,836	$9.00 to $14.77

In addition, options totaling 86,411, 218,130 and 162,565 expired or were forfeited during the years ended December 31, 2018, 2017 and 2016, respectively.

Options outstanding and exercisable at December 31, 2018, 2017 and 2016 were as follows:

Year	Outstanding		Range of Exercise Prices	Exercisable		Weighted Average Exercise Price
2018		965,659	$10.10 to $21.30		521,202	$	16.08
2017		988,167	$9.97 to $20.93		539,993	$	16.23
2016		1,183,830	$9.97 to $20.93		934,898	$	14.88

The fair value of options granted is estimated using an option pricing model based on the assumptions set forth in the following table. The Company uses historical data to estimate employee exercise and departure behavior. The risk free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant and through the expected term. The dividend yield rate is based on the Company’s historical dividend yield. The expected volatility is derived from historical volatility of the Company’s shares and those of similar companies measured against the market as a whole. The Company used the binomial lattice option pricing model based on the assumptions set forth in the following table.

	2018			2017			2016
Risk free interest rate		2.90	%		2.50	%		1.80	%
Expected dividend yield		2.50	%		3.80	%		4.60	%
Expected life of award (years)		4.00			4.10			8.00
Expected volatility		42.50	%		50.00	%		50.00	%
Fair value per option	$	6.30		$	4.47		$	3.45

The following table provides a summary of stock option activity for the period ended December 31, 2018:

	Shares			Average Exercise Price		Weighted Average Life (in Years)
Outstanding at December 31, 2017		988,167		$	15.13
Options granted		255,072			21.30
Options exercised		(191,169	)		14.30
Canceled or forfeited		(86,411	)		17.65
Expired		—			—
Outstanding at December 31, 2018		965,659			16.69		7.23
Exercisable at December 31, 2018		521,202		$	16.08		6.10

The intrinsic value of a stock option is the amount by which the market value of the underlying stock exceeds the exercise price of the option. The intrinsic value of stock options exercised in 2018, 2017 and 2016 was $1,745, $2,813 and $1,809, respectively.

The following table provides a summary of restricted stock units, including performance-based restricted stock units, and restricted stock activity for the year ended December 31, 2018:

	Shares			Average Grant-Date Fair Value
Unvested shares at December 31, 2017		412,650
Granted		178,005		$	21.65
Vested		(104,737	)		14.09
Forfeited		(62,123	)		16.94
Unvested shares at December 31, 2018		423,795

Restricted stock units are rights to receive shares of common stock, subject to forfeiture and other restrictions, which vest over a one or three year period. Restricted stock units are considered to be non-vested shares under the accounting guidance for share-based payment and are not reflected as issued and outstanding shares until the restrictions lapse. At that time, the shares are released to the grantee and the Company records the issuance of the shares. Restricted stock awards are valued based on the market price of the underlying shares on the grant date. Compensation expense is recognized on a straight-line basis over the requisite service period. At December 31, 2018, restricted stock awards had vesting periods up through March 2021.

Included in the December 31, 2018 unvested shares are 268,103 performance-based restricted stock units. The fair value of these awards is calculated using the market price of the underlying common stock on the date of grant. In determining fair value, the Company does not take into account performance-based vesting requirements. For these awards, the performance-based vesting requirements determines the number of shares that ultimately vest, which can vary from 0% to 200% of target depending on the level of achievement of established performance criteria. Compensation expense is recognized over the requisite service period subject to adjustment based on the probable number of shares expected to vest under the performance condition.

Stock compensation expense was approximately $4,257, $3,626 and $3,357 for the years ended December 31, 2018, 2017 and 2016, respectively. These expenses are included in general and administrative expenses in the accompanying Consolidated Statements of Operations. Total unrecognized compensation cost related to non-vested share based compensation arrangements at December 31, 2018 was approximately $4,737 which will be recognized over the next three years, as such compensation is earned.