Stock options to purchase 574,500, 603,500 and 3,358,250 shares of common stock were excluded from the computation of diluted earnings per share during the years ended December 31, 2018, 2017 and 2016, respectively, as their effect would have been anti-dilutive. 2,500 shares of unvested restricted stock were excluded from the computation of diluted earnings per share during the year ended December 31, 2018 as their effect would have been anti-dilutive.