stock-based compensation 2013 we have several stock-based compensation plans under which employees and non-employee directors receive stock options , nonvested retention shares , and nonvested stock units . we refer to the nonvested shares and stock units collectively as 201cretention awards 201d . we issue treasury shares to cover option exercises and stock unit vestings , while new shares are issued when retention shares vest . we adopted fasb statement no . 123 ( r ) , share-based payment ( fas 123 ( r ) ) , on january 1 , 2006 . fas 123 ( r ) requires us to measure and recognize compensation expense for all stock-based awards made to employees and directors , including stock options . compensation expense is based on the calculated fair value of the awards as measured at the grant date and is expensed ratably over the service period of the awards ( generally the vesting period ) . the fair value of retention awards is the stock price on the date of grant , while the fair value of stock options is determined by using the black-scholes option pricing model . we elected to use the modified prospective transition method as permitted by fas 123 ( r ) and did not restate financial results for prior periods . we did not make an adjustment for the cumulative effect of these estimated forfeitures , as the impact was not material . as a result of the adoption of fas 123 ( r ) , we recognized expense for stock options in 2006 , in addition to retention awards , which were expensed prior to 2006 . stock-based compensation expense for the year ended december 31 , 2006 was $ 22 million , after tax , or $ 0.08 per basic and diluted share . this includes $ 9 million for stock options and $ 13 million for retention awards for 2006 . before taxes , stock-based compensation expense included $ 14 million for stock options and $ 21 million for retention awards for 2006 . we recorded $ 29 million of excess tax benefits as an inflow of financing activities in the consolidated statement of cash flows for the year ended december 31 , 2006 . prior to the adoption of fas 123 ( r ) , we applied the recognition and measurement principles of accounting principles board opinion no . 25 , accounting for stock issued to employees , and related interpretations . no stock- based employee compensation expense related to stock option grants was reflected in net income , as all options granted under those plans had a grant price equal to the market value of our common stock on the date of grant . stock-based compensation expense related to retention shares , stock units , and other incentive plans was reflected in net income . the following table details the effect on net income and earnings per share had compensation expense for all of our stock-based awards , including stock options , been recorded in the years ended december 31 , 2005 and 2004 based on the fair value method under fasb statement no . 123 , accounting for stock-based compensation . pro forma stock-based compensation expense year ended december 31 , millions of dollars , except per share amounts 2005 2004 .
what was the percentage difference of earnings per share 2013 basic pro forma compared to earnings per share 2013 diluted pro forma in 2005?
[a] stock options for executives granted in 2003 and 2002 included a reload feature . this reload feature allowed executives to exercise their options using shares of union pacific corporation common stock that they already owned and obtain a new grant of options in the amount of the shares used for exercise plus any shares withheld for tax purposes . the reload feature of these option grants could only be exercised if the .