We recognized share-based payment expense of $19,417 and $18,240 for the three months ended March 31, 2015 and 2014, respectively.

2009 Long-Term Stock Incentive Plan

In May 2009, our stockholders approved the Sirius XM Radio Inc. 2009 Long-Term Stock Incentive Plan (the “2009 Plan”).  Employees, consultants and members of our board of directors are eligible to receive awards under the 2009 Plan.  The 2009 Plan provides for the grant of stock options, restricted stock awards, restricted stock units and other stock-based awards that the compensation committee of our board of directors may deem appropriate.  Vesting and other terms of stock-based awards are set forth in the agreements with the individuals receiving the awards.  Stock-based awards granted under the 2009 Plan are generally subject to a vesting requirement.  Stock options generally expire ten years from the date of grant.  Each restricted stock unit entitles the holder to receive one share of common stock upon vesting.  As of March 31, 2015, 21,668 shares of common stock were available for future grants under the 2009 Plan.

Other Plans

We maintain three other share-based benefit plans — the XM 2007 Stock Incentive Plan, the Amended and Restated Sirius Satellite Radio 2003 Long-Term Stock Incentive Plan and the XM 1998 Shares Award. No further awards may be made under these plans, and all outstanding awards are fully vested.

The following table summarizes the weighted-average assumptions used to compute the fair value of options granted to employees and members of our board of directors:

There were no options granted to employees or members of our board of directors during the three months ended March 31, 2015.  There were no options granted to third parties during the three months ended March 31, 2015 and 2014.  We do not intend to pay regular dividends on our common stock.  Accordingly, the dividend yield percentage used in the Black-Scholes-Merton option value was zero for all periods.

The following table summarizes stock option activity under our share-based plans for the three months ended March 31, 2015:

The weighted average grant date fair value per share of options granted during the three months ended March 31, 2014 was $1.08.  The total intrinsic value of stock options exercised during the three months ended March 31, 2015 and 2014 was $30,952 and $11,528, respectively.  During the three months ended March 31, 2015, the number of shares which were issued as a result of stock option exercises was 4,837.

We recognized share-based payment expense associated with stock options of $16,691 and $16,615 for the three months ended March 31, 2015 and 2014, respectively.

The following table summarizes the nonvested restricted stock unit activity under our share-based plans for the three months ended March 31, 2015:

The weighted average grant date fair value per share of restricted stock units granted during the three months ended March 31, 2014 was $3.70.  There was no vesting of restricted stock units during three months ended March 31, 2015 and 2014.

We recognized share-based payment expense associated with restricted stock units of $2,726 and $1,625 during the three months ended March 31, 2015 and 2014, respectively.

Total unrecognized compensation costs related to unvested share-based payment awards for stock options and restricted stock units granted to employees and members of our board of directors at March 31, 2015 and December 31, 2014, net of estimated forfeitures, were $142,748 and $162,985, respectively.  The total unrecognized compensation costs at March 31, 2015 are expected to be recognized over a weighted-average period of 2.5 years.

401(k) Savings Plan

Sirius XM sponsors the Sirius XM Radio Inc. 401(k) Savings Plan (the “Sirius XM Plan”) for eligible employees. The Sirius XM Plan allows eligible employees to voluntarily contribute from 1% to 50% of their pre-tax eligible earnings, subject to certain defined limits. We match 50% of an employee’s voluntary contributions per pay period on the first 6% of an employee’s pre-tax salary up to a maximum of 3% of eligible compensation.  Employer matching contributions under the Sirius XM Plan vest at a rate of 33.33% for each year of employment and are fully vested after three years of employment for all current and future contributions.  Beginning in January 2014, our cash employer matching contributions were no longer used to purchase shares of our common stock on the open market, unless the employee elects our common stock as their investment option for this contribution.  We contributed $3,027 and $1,879 during three months ended March 31, 2015 and 2014, respectively, to the Sirius XM Plan in fulfillment of our matching obligation.