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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: 

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## Accounting for Stock-Based Compensation Awards 

The following table summarizes our stock-based compensation expense and the related income tax benefit we recorded in the past three years: 

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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 

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: 

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