NOTES TO CONSOLIDATED FINANCIAL STATEMENTS Q. STOCK COMPENSATION PLANS  December 31, 2011, 2008 and 2009 (currencies in millions except per share amounts) PACCAR has certain plans under which officers and key employees may be granted options to purchase shares of  the Company’s authorized but unissued common stock under plans approved by stockholders. Non-employee  directors and certain officers may be granted restricted shares of the Company’s common stock under plans  approved by stockholders. Options outstanding under these plans were granted with exercise prices equal to the fair  market value of the Company’s common stock at the date of grant. Options expire no later than ten years from the  grant date and generally vest after three years. Restricted stock awards generally vest over three years or earlier upon  meeting certain age and service requirements.  The Company recognizes compensation cost on these options and restricted stock awards on a straight line basis  over the requisite period the employee is required to render service. The maximum number of shares of the  Company’s common stock authorized for issuance under these plans is 46.7 million shares and as of  December 31, 2011, the maximum number of shares available for future grants was 18.3 million.  The estimated fair value of each option award is determined on the date of grant using the Black-Scholes-Merton  option pricing model that uses assumptions noted in the following table. The risk free interest rate is based on the  U.S. Treasury yield curve in effect at the time of grant. Expected volatility is based on historical volatility. The  dividend yield is based on an estimated future dividend yield using projected net income for the next five years,  implied dividends and Company stock price. The expected term is based on the period of time that options granted  are expected to be outstanding based on historical experience.  The fair value of options granted was $10.9, $11.7 and $10.0 for the years ended December 31, 2011, 2010 and  2009, respectively. A summary of activity under the Company’s stock plans is presented below. 2011  2010  2009 Risk-free interest rate 2.22% 2.48%  2.00% Expected volatility 45% 44%  39% Expected dividend yield 2.8% 2.5%  3.0% Expected term  5 years 5 years  5 years Weighted average grant date fair value of options per share  $16.45 $11.95  $8.47 2011  2010 2009 Intrinsic value of options exercised  $13.5 $33.7  $22.7 Cash received from stock option exercises  10.9 22.0  17.6 Tax benefit related to stock option exercises  4.7 10.8  7.1 Stock based compensation  13.8 8.5  9.5 Tax benefit related to stock based compensation  5.2 3.2  3.5