Note 14. Stock‑Based Compensation

Stock Options

The following is a summary of stock option activity under the Plans:


				Weighted
		Weighted		average
		average		remaining	Aggregate
	Outstanding	exercise price		contractual life	Intrinsic Value
	Options	per share		(Years)	(in thousands)
Outstanding at December 31, 2016	5,997,372	$	10.18	7.30	$	145,270
Granted	577,690		34.77
Forfeited	(191,890)		18.75
Exercised	(1,562,590)		7.34
Expired	(2,893)		13.79
Outstanding at September 30, 2017	4,817,689	$	13.70	6.93	$	107,478

Vested and exercisable at September 30, 2017	3,313,087	$	10.34	6.28	$	84,939

Aggregate intrinsic value represents the difference between our estimated fair value of common stock and the exercise price of outstanding in‑the‑money options. The fair value per share of common stock was $35.98 as of September 30, 2017 based upon the closing price of our common stock on the NYSE. The total intrinsic value of stock options exercised was $6,025 and $47,915 for the three and nine months ended September 30, 2017, respectively, and insignificant for each of the three and nine months ended September 30, 2016.

Restricted Stock Units

The following is a summary of RSU activity under the 2016 Plan:


		Weighted
		average
		grant date fair value
	Number of Awards	per share
Outstanding at December 31, 2016	67,295	$	25.88
Granted	275,726		34.98
Forfeited	(32,796)		31.03
Vested and converted to shares	(38,302)		29.88
Outstanding at September 30, 2017	271,923	$	33.93
Expected to vest at September 30, 2017	271,923	$	33.93

Restricted Stock

We issued an aggregate of 768,021 shares of restricted common stock to certain employees of RowdMap at a fair market value of $43.27 per share. Half of these shares are subject to continued employment and performance-based vesting requirements and, if achieved, will vest on the one year anniversary of the closing date of the RowdMap Acquisition. The other half are subject to continued employment with us, with one-third vesting on each of the first three anniversaries of the closing of the RowdMap Acquisition.

Employee Stock Purchase Plan

We have an ESPP, which became effective January 1, 2017, for US and non-US employees (collectively, “ESPP”), both of which have a series of six month offering periods, with a new offering period beginning on the first day of January and July each year. The ESPP was adopted by our Board of Directors in August 2016 and approved by shareholders in May 2017. Employees may contribute up to 10% of their pay towards the purchase of common stock via payroll deductions to a maximum of $10 per year, or $5 per offering period. Purchase dates occur on the last business day of June and December of each year and shares are purchased at a 10% discount off the closing price on the NYSE on the date of purchase. On June 30, 2017, 29,668 shares were purchased at a price of $33.43. Employees must hold the shares purchased for a minimum of 90 days.

Stock Compensation Expense

We used the weighted average assumptions to estimate the fair value of stock options granted for the periods presented as follows:


	Nine Months Ended September 30,
	2017			2016
Expected term (years)		6.25			6.25
Expected volatility		40.00	%		50.00	%
Expected dividend yield		0.00	%		0.00	%
Weighted average risk-free interest rate		1.92	%		1.34	%
Weighted average grant date fair value	$	14.60		$	9.39

Total fair market value related to the restricted stock issued in connection with the RowdMap Acquisition is $33,232 based on the closing price of our common stock on the date of grant. For the time-based shares, stock-based compensation expense is being recorded ratably over the three year vesting period. For the performance-based shares, stock-based compensation expense will be recorded over the one year vesting period to the extent it is probable the performance criteria will be achieved. As of September 30, 2017, we recorded approximately $2,769 in stock-based compensation expense related to the performance awards that we estimate are probable of achieving the performance criteria.

We recorded total stock‑based compensation expense of $5,752 and $17,042 for the three months ended September 30, 2017 and 2016, respectively, and $10,290 and $21,544 for the nine months ended September 30, 2017 and 2016, respectively. Stock-based compensation expense for the three and nine months ended September 30, 2016 includes $15,898 related to the vesting of substantially all then outstanding performance based stock options. Stock-based compensation expense during the nine months ended September 30, 2016 also includes $2,257 related to the accelerated vesting of certain stock options as a result of our IPO. As of September 30, 2017, we had total unrecognized compensation cost related to 2,467,744 unvested stock options and RSUs under the Plans as well as restricted stock of $46,658 which we expect to recognize over the next 2.6 years.