Stock Compensation Plans (Tables)

The following table summarizes stock option activity of the Company during the three months ended March 31, 2015 (shares in thousands):



	Shares Subject to Options (in thousands)	Weighted-Average Exercise Price per Share
As of December 31, 2014	11,116	$4.96
Granted	1,349	$3.49
Exercised	(76)	$2.81
Forfeitures and cancellations	(559)	$4.14
Outstanding at March 31, 2015	11,830	$4.85
Options exercisable at March 31, 2015	7,821	$5.57

The following table summarizes activity related to restricted stock awards and restricted stock units of the Company during the three months ended March 31, 2015:



	Number of Shares (in thousands)	Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2014	1,674	$2.99
Grants and awards	1,005	$3.49
Vested and released	(494)	$3.56
Forfeitures and cancellations	(134)	$3.27
Outstanding at March 31, 2015	2,051	$3.08

Following are the weighted-average underlying assumptions used to determine the fair value of stock option award grants and for stock purchase rights under the ESPP for the periods indicated:



	Three Months Ended
	March 31,
Stock Option Grants	2015			2014
Risk-free interest rate	1.7		%	2.0		%
Volatility	92.1		%	94.0		%
Dividend yield	—		%	—		%
Expected life (years)	7.2			7.1
Weighted-average grant date fair value	$	2.78		$	1.93



	Three Months Ended
	March 31,
ESPP Stock Purchase Rights	2015			2014
Risk-free interest rate	0.14		%	0.09		%
Volatility	55.7		%	74.2		%
Dividend yield	—		%	—		%
Expected life (years)	0.5			0.5
Weighted-average grant date fair value	$	1.07		$	0.77