12. Equity Incentive Plan

Our Board of Directors has adopted and, with the approval of our stockholders, amended the 2010 Equity Incentive Plan (as amended, the "2010 Plan"). The 2010 Plan is administered by the Compensation Committee of the Board of Directors. Awards issuable under the 2010 Plan include common stock, stock options, restricted stock, stock appreciation rights, dividend equivalents, Operating Partnership units and other incentive awards. We have reserved a total of 6,000,000 shares of our common stock for issuance pursuant to the 2010 Plan, which may be adjusted for changes in our capitalization and certain corporate transactions. To the extent that an award expires, terminates or lapses, or an award is settled in cash without the delivery of shares of common stock to the participant, then any unvested shares subject to the award will be available for future grant or sale under the 2010 Plan. Shares of restricted stock which are forfeited or repurchased by us pursuant to the 2010 Plan may again be awarded under the 2010 Plan. The payment of dividend equivalents in cash in conjunction with any outstanding awards will not be counted against the shares available for issuance under the 2010 Plan.

As of December 31, 2015, 3,359,814 shares of our common stock were available for issuance pursuant to the 2010 Plan.

Stock Options

Stock option awards are granted with an exercise price equal to the closing market price of the Company's common stock on the date of grant. The fair value of each option granted under the 2010 Plan is estimated on the date of grant using the Black-Scholes option-pricing model. The fair values are amortized on a straight-line basis over the vesting periods.

The following table sets forth stock option activity under the 2010 Plan for the years ended December 31, 2015, 2014, and 2013:

	Number of Shares Subject to Option			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value
Options outstanding, December 31, 2012		1,017,195		$	17.25	8.2 years	$10.6 million
Granted		209,268			32.50
Exercised		(54,781	)		16.86		$1.0 million
Forfeited		(37,232	)		23.00
Expired		(535	)		34.82

Options outstanding, December 31, 2013		1,133,915		$	19.89	7.6 years	$14.0 million
Granted		—			—
Exercised		(307,022	)		16.10		$5.6 million
Forfeited		(64,851	)		25.83
Expired		(3,947	)		15.80

Options outstanding, December 31, 2014		758,095		$	20.94	6.7 years	$13.7 million
Granted		—			—
Exercised		(410,322	)		20.15		$12.0 million
Forfeited		(7,281	)		27.53
Expired		(282	)		15.23

Options outstanding, December 31, 2015		340,210		$	21.77	5.8 years	$11.9 million


Exercisable at December 31,
2013		498,176		$	16.51	7.1 years	$7.8 million
2014		474,132		$	18.78	6.4 years	$9.6 million
2015		234,943		$	18.47	5.4 years	$9.0 million

The following table sets forth the number of shares subject to options that are unvested as of December 31, 2015, 2014, and 2013, and the fair value of these options at the grant date:

	Number of Shares Subject to Option			Weighted Average Fair Value at Grant Date
Unvested balance, December 31, 2012		730,159		$	5.70
Granted		209,268			10.01
Forfeited		(37,232	)		7.21
Vested		(266,456	)		5.54

Unvested balance, December 31, 2013		635,739		$	7.10
Granted		—			—
Forfeited		(64,851	)		8.03
Vested		(286,924	)		6.25

Unvested balance, December 31, 2014		283,964		$	7.75
Granted		—			—
Forfeited		(7,281	)		8.48
Vested		(171,416	)		6.86

Unvested balance, December 31, 2015		105,267		$	9.13

As of December 31, 2015, total unearned compensation on options was approximately $0.4 million, and the weighted-average vesting period was 1.0 years. As the Company has been a publicly traded company only since September 28, 2010, expected volatilities used in the Black-Scholes model are based on the historical volatility of a group of comparable REITs. We utilize the simplified method of estimating the term for options granted due to the lack of historical exercise data necessary to provide a reasonable basis upon which to estimate the term. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. No options were granted during the years ended 2015 or 2014. The following table summarizes the assumptions used to value the stock options granted during the year ended December 31, 2013:

	2013
Expected term (in years)		6.25
Expected volatility		43.86	%
Expected annual dividend		3.33	%
Risk-free rate		1.26	%

Restricted Awards and Units

Restricted stock awards and restricted stock units, or RSUs, are granted with a fair value equal to the closing market price of the Company's common stock on the date of grant. The principal difference between restricted stock awards and RSUs is that RSUs are not shares of our common stock and do not have any of the rights or privileges thereof, including voting rights. On the applicable vesting date, the holder of an RSU becomes entitled to a share of common stock. The restricted stock awards and RSUs are amortized on a straight-line basis to expense over the vesting period. The following table sets forth the number of unvested restricted stock and RSUs and the weighted-average fair value of these awards at the date of grant:

	Restricted Awards and Units			Weighted Average Fair Value at Grant Date
Unvested balance, December 31, 2012		598,695		$	21.37
Granted		194,302			32.43
Forfeited		(58,199	)		28.44
Vested		(239,647	)		20.96

Unvested balance, December 31, 2013		495,151		$	25.08
Granted		216,175			31.51
Forfeited		(109,798	)		27.64
Vested		(207,512	)		22.79

Unvested balance, December 31, 2014		394,016		$	29.10
Granted		187,644			47.41
Forfeited		(34,788	)		36.06
Vested		(169,260	)		26.96

Unvested balance, December 31, 2015		377,612		$	38.51

As of December 31, 2015, total unearned compensation on restricted awards was approximately $10.0 million, and the weighted-average vesting period was 2.3 years.

Performance Stock Awards

We grant long-term incentives to members of management in the form of performance-based restricted stock awards ("PSAs") under the 2010 Plan. The number of PSAs earned is based on our achievement of relative total shareholder return ("TSR") measured versus the MSCI US REIT Index over a three-year performance period, and the number of shares earned under the PSAs may range from 0% to 150% for 2014 grants and from 25% to 175% for 2015 grants. The PSAs are earned as follows: (i) 20% of the PSAs are eligible to be earned upon TSR achievement in year one of the performance period, (ii) 20% of the PSAs are eligible to be earned upon TSR achievement in year two of the performance period, (iii) 20% of the PSAs are eligible to be earned upon TSR achievement in year three of the performance period, and (iv) 40% of the PSAs are eligible to be earned upon a cumulative TSR achievement over the three-year performance period. The PSAs have a service condition and will be released at the end of the three-year performance period, to the extent earned, provided that the holder continues to be employed by the Company at the end of the three-year performance period. Holders of the PSAs are entitled to dividends on the PSAs, which will be accrued and paid in cash at the end of the three-year performance period. The PSAs initially are granted and issued at the highest potential percentage of target amount and thereafter are forfeited to the extent vesting conditions are not met.

On March 4, 2014, we granted 91,335 PSAs, equal to 150% of the target amount, with an aggregate fair value of $1.6 million on the grant date. The PSAs, in addition to a service condition, are subject to our performance versus the MSCI US REIT Index which is a market condition and impacts the number of shares that ultimately vests. Upon evaluating the results of the market condition, the final number of shares is determined and such shares vest based on satisfaction of the service condition. The PSAs are amortized on a straight-line basis over the vesting period. During the years ended December 31, 2015, and 2014, 7,273 and 5,484 of the PSAs granted in March 2014 were forfeited due to termination of service, respectively. During the year ended December 31, 2015, 6,444 PSAs were not achieved due to performance against the MSCI REIT Index correlating to less than 150% of the target amount during the first year of the performance period.

On March 3, 2015, we granted 78,553 PSAs, equal to 175% of the target amount, with an aggregate value of $2.7 million on the grant date. The PSAs, in addition to a service condition, are subject to our performance versus the MSCI US REIT Index, which is a market condition and impacts the number of shares that ultimately vests. Upon evaluating the results of the market condition, the final number of shares is determined and such shares vest based on satisfaction of the service condition. The PSAs are amortized on a straight-line basis over the vesting period. During the year ended December 31, 2015, 7,129 of the PSAs granted in March 2015 were forfeited due to termination of service.

As of December 31, 2015, total unearned compensation on PSAs was approximately $2.4 million, and the weighted-average vesting period was 2.0 years. The fair value of each PSA award is estimated on the date of grant using a Monte Carlo simulation. The simulation requires assumptions for expected volatility, risk-free rate of return, and dividend yield. The following table summarizes the assumptions used to value the PSAs granted during the years ended December 31, 2015, and 2014:

	2015			2014
Expected term (in years)		2.83			2.83
Expected volatility		25.51	%		32.98	%
Expected annual dividend		—			—
Risk-free rate		1.02	%		0.64	%