Stock Plans (Tables)

Stock-based compensation cost included in cost of revenue; selling, general and administrative expense; and research and development expense is as follows (in thousands):



	Three Months Ended March 31,
	2017		2016
Cost of revenue	$	193	$	235
Selling, general and administrative	1,069		671
Research and development	276		297
Total stock-based compensation expense	$	1,538	$	1,203

The following table summarizes the amount of compensation expense recognized for RSUs for the three months ended March 31, 2017 and 2016 (in thousands):



	Three Months Ended March 31,
RSU Type	2017		2016
Service-based	$	667	$	533
Performance objectives	6		12
Market-condition	192		191
	$	865	$	736

The fair value of the market-condition PSUs granted was calculated using a Monte Carlo valuation model with the following assumptions:



	Three Months Ended March 31,
	2017		2016
Expected dividend yield	—	%	—	%
Expected volatility	53	%	62	%
Risk-free interest rate	1.55	%	1.07	%
Expected term (in years)	2.8		3.0

The fair value of the ESPP shares for the three and three months ended March 31, 2017 and 2016 was estimated using the Black-Scholes valuation model for a call and a put option with the following weighted-average assumptions:



	Three Months Ended March 31,
	2017			2016
Expected dividend yield	—		%	—		%
Expected volatility	29		%	60		%
Risk-free interest rate	0.62		%	0.49		%
Expected term (in years)	0.5			0.5
Fair value per share	$	1.19		$	2.27