Plan. Joe Mansueto, our chairman and chief executive officer, does  not participate in the 2004 Stock Incentive Plan or prior plans. Since  the adoption of the 2004 Stock Incentive Plan, we have granted  stock options and, beginning in 2006, restricted stock units. Prior to November 2004, we granted stock options under various  plans, including the 1993 Stock Option Plan, the 2000 Morningstar  Stock Option Plan, and the 2001 Morningstar Stock Option Plan  (collectively, the Prior Plans). The 2004 Stock Incentive Plan amends  and restates the Prior Plans. Under the 2004 Stock Incentive Plan,  we will not grant any additional options under any of the Prior Plans,  and any shares subject to an award under any of the Prior Plans  that are forfeited, canceled, settled, or otherwise terminated with- out a distribution of shares, or withheld by us in connection with  the exercise of options or in payment of any required income tax  withholding, will not be available for awards under the 2004 Stock  Incentive Plan. The following table summarizes the number of shares available for  future grants under our 2004 Stock Incentive Plan: In accordance with FASB ASC 718,  Compensation—Stock  Compensation , we estimate forfeitures of all employee stock-based  awards and recognize compensation cost only for those awards  expected to vest. Because our largest annual equity grants typically  have vesting dates in the second quarter, we adjust the stock-based  compensation expense at that time to reflect those awards that  ultimately vested and update our estimate of the forfeiture rate that  will be applied to awards not yet vested. Restricted stock units represent the right to receive a share of  Morningstar common stock when that unit vests. Restricted stock  units granted under the 2004 Stock Incentive Plan generally vest  ratably over a four-year period. For restricted stock units granted  through December 31, 2008, employees could elect to defer receipt  of the Morningstar common stock issued upon vesting of the  restricted stock unit. We measure the fair value of our restricted stock units on the date  of grant based on the closing market price of the underlying common  stock on the day prior to grant. We amortize that value to stock- based compensation expense, net of estimated forfeitures, ratably  over the vesting period. The following table summarizes restricted  stock unit activity during the past three years: The following table summarizes our stock-based compensation  expense and the related income tax benefit we recorded in the past  three years: Accounting for Stock-Based Compensation Awards As of December 31 (000)  2010 2009 Shares available for future grants  1,600 2,143 ($000)  2010 2009  2008 Restricted stock units  $ 12,545 $ 10,591  $ 7,571 Restricted stock  1,248 —  — Stock options  — 1,002  3,710 Total stock-based compensation expense  $ 13,793 $11,593  $ 11,281 Income tax benefit related to the $ 3,500 $ 3,625  $ 3,544 stock-based compensation expense  Weighted  Average  Vested  Grant but  Date  Restricted Stock Units (RSUs)   Unvested  Deferred  Total  Value RSUs outstanding—  414,282  6,621   420,903  $ 48.41  January 1, 2008 Granted  213,623  —  213,623   63.96 Vested   (96,187)  —   (96,187)   47.89 Vested but deferred   (15,403)  15,403  —  — Forfeited  (21,815)  —  (21,815)   50.26 RSUs outstanding—   494,500  22,024  516,524   55.17  December 31, 2008  Granted   373,829  —   373,829   38.89 Vested   (150,031)  —   (150,031)   53.27 Vested but deferred   (17,570)  17,570  —  — Forfeited   (19,303)  —   (19,303)   50.05 RSUs outstanding—  681,425  39,594  721,019   46.99 December 31, 2009  Granted   399,349  —   399,349   47.76 Vested   (232,292)  —   (232,292)   47.77 Vested but deferred   (16,748)  16,748  —  — Issued  —  (11,153)  (11,153)   49.29 Forfeited   (54,068)  —   (54,068)   46.70 RSUs outstanding—  December 31, 2010 777,666  45,189   822,855   47.14 Restricted Stock Units Morningstar, Inc. 2010 Annual Report 129