Stock-based Compensation | 7. Stock-based Compensation The fair value of stock options granted was estimated at the date of grant using the following weighted-average assumptions: Three Months Ended Nine Months Ended 2017 2016 2017 2016 Expected life in years 6.2 6.2 6.1 6.1 Risk-free interest rate 2.11 % 1.35 % 2.08 % 1.41 % Volatility 42 % 45 % 42 % 45 % Dividend yield — — — — Weighted-average fair value of stock options granted $ 3.03 $ 4.98 $ 3.07 $ 4.17 The Company recorded stock-based compensation expense of $1,818 and $1,681 for the three months ended September 30, 2017 and 2016, respectively, and $5,294 and $4,265 for the nine months ended September 30, 2017 and 2016, respectively. In July 2017, the Company entered into a separation agreement with its former Chief Executive Officer (“CEO”), which accelerated the vesting schedule of certain existing stock-based awards held by the CEO. The incremental stock-based compensation expense as a result of the modification of these stock-based awards was $186 for the three months ended September 30, 2017. Further, the vesting schedule of certain other stock-based awards held by the CEO accelerates upon a change in control of the Company on or prior to December 31, 2017, which would result in an additional $220 of stock-based compensation expense upon such change in control. As of September 30, 2017, there was $20,389 of unrecognized stock-based compensation expense related to stock-based awards that is expected to be recognized over a weighted-average period of 2.26 years. On January 1, 2017, the Company adopted ASU No. 2016-09. 2016-09 paid-in-capital The following is a summary of the status of the Company’s stock options as of September 30, 2017 and the stock option activity during the nine months ended September 30, 2017. Number of Weighted-Average Weighted- Aggregate Outstanding at December 31, 2016 4,150,584 $ 7.17 Granted 472,727 7.00 Exercised (198,555 ) 1.91 $ 1,159 Canceled (270,498 ) 8.42 Outstanding at September 30, 2017 4,154,258 $ 7.32 6.48 $ 4,182 Exercisable at September 30, 2017 2,275,052 $ 7.22 4.93 $ 3,212 (1) The aggregate intrinsic value was calculated based on the positive difference between the fair value of the Company’s common stock on September 30, 2017 of $7.20 per share, or the date of exercise, as appropriate, and the exercise price of the underlying options. The following table summarizes the restricted stock unit activity during the nine months ended September 30, 2017: Shares Weighted Unvested by December 31, 2016 1,902,577 $ 7.84 Granted 1,154,473 6.91 Vested and issued (415,586 ) 7.64 Canceled (229,030 ) 8.02 Unvested by September 30, 2017 2,412,434 $ 7.40 |