Our 2004 Equity Incentive Plan (the “2004 Plan”) authorizes the granting of options to purchase shares of our Class B common stock, restricted stock units ("RSUs") and other stock-based awards to our employees, consultants, officers and directors. Our 2013 Equity Incentive Plan (the “2013 Plan” and, together with the 2004 Plan, the “Plans”), which was a successor to our 2004 Plan, authorizes the granting of options to purchase shares of our Class A common stock, RSUs and other stock-based awards to our employees, consultants, officers and directors.

Options granted under the Plans may be incentive or nonstatutory stock options. Incentive stock options may only be granted to employees. The term of each option is stated in the award agreement, but shall be no more than ten years from the date of grant. Options typically vest over a period of four years.

RSUs entitle the holder to receive shares of Class A common stock as the award vests. RSUs typically vest over a period of four years. The fair value of an RSU is determined by using the closing price of our Class A common stock as reported on the New York Stock Exchange on the date of grant. The Company's non-vested RSUs do not have nonforfeitable rights to dividends or dividend equivalents.

The summary of shares available for issuance for equity based awards (including stock options and RSUs) during the three months ended March 31, 2015 is as follows: