(8) Share-based Compensation

The Company’s 2013 Stock Incentive Plan (as amended, the “2013 Equity Plan”) authorizes the issuance of various types of share-based awards to the Company’s employees, officers, directors, and other eligible participants. In March 2018, the Board of Directors authorized, subject to stockholder approval, a further amendment to the 2013 Equity Plan to, among other things, increase the total number of shares of the Company’s class A common stock authorized for issuance under the 2013 Equity Plan from 1,700,000 shares to 2,300,000 shares (“Amendment No. 4”). The Company considers stockholder approval of Amendment No. 4 to the 2013 Equity Plan to be perfunctory since the Company’s Chairman, President & Chief Executive Officer holds a majority of the total voting power of all the Company’s outstanding voting stock.

During the first quarter of 2018, stock options to purchase an aggregate of 475,000 shares of class A common stock were granted pursuant to the 2013 Equity Plan. As of March 31, 2018, there were options to purchase 1,462,883 shares of class A common stock outstanding under the 2013 Equity Plan. As of March 31, 2018, there were 613,750 remaining shares of class A common stock authorized for future issuance under the 2013 Equity Plan, 600,000 of which are subject to stockholder approval of Amendment No. 4.

The following table summarizes the Company’s stock option activity (in thousands, except per share data and years) for the three months ended March 31, 2018:

	Stock Options Outstanding
				Weighted Average		Aggregate		Weighted Average
				Exercise Price		Intrinsic		Remaining Contractual
	Shares			Per Share		Value		Term (Years)
Balance as of January 1, 2018		992		$	145.28
Granted		475			131.71
Exercised		0			0.00	$	0
Forfeited/Expired		(4	)		165.01
Balance as of March 31, 2018		1,463		$	140.83
Exercisable as of March 31, 2018		587		$	138.98	$	3,029		6.5
Expected to vest as of March 31, 2018		876		$	142.06		1,085		8.8
Total		1,463		$	140.83	$	4,114		7.9

Stock options outstanding as of March 31, 2018 are comprised of the following range of exercise prices per share (in thousands, except per share data and years):

	Stock Options Outstanding at March 31, 2018
			Weighted Average		Weighted Average
			Exercise Price		Remaining Contractual
Range of Exercise Prices per Share	Shares		Per Share		Term (Years)
$117.85 - $120.00		25	$	118.55		6.1
$120.01 - $150.00		1,045	$	126.78		8.0
$150.01 - $180.00		198	$	167.55		6.9
$180.01 - $201.25		195	$	191.78		8.4
Total		1,463	$	140.83		7.9

An aggregate of 55,000 stock options with an aggregate fair value of $4.0 million vested during the three months ended March 31, 2018. The weighted average grant date fair value of stock option awards using the Black-Scholes pricing model was $52.44 and $77.31 for each share subject to a stock option granted during the three months ended March 31, 2018 and 2017, respectively, based on the following assumptions:

	Three months ended
	March 31,
	2018			2017
Expected term of options in years	6.3			6.3
Expected volatility	35.2 - 35.5%				37.8	%
Risk-free interest rate		2.7	%		2.3	%
Expected dividend yield		0.0	%	0.0%

For the three months ended March 31, 2018 and 2017, the Company recognized approximately $4.7 million and $3.1 million, respectively, in share-based compensation expense from stock options granted under the 2013 Equity Plan. As of March 31, 2018, there was approximately $40.0 million of total unrecognized share-based compensation expense related to unvested stock options. The Company expects to recognize this remaining share-based compensation expense over a weighted average vesting period of approximately 3.3 years.