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 year ended december 31 , 2005 based on the fair value method under fasb statement no . 123 , accounting for stock-based compensation . pro forma stock-based compensation expense millions of dollars , except per share amounts 2005 .

Table: pro forma stock-based compensation expensemillions of dollars except per share amounts 2005 net income as reported $ 1026 stock-based employee compensation expense reported in net income net of tax 13 total stock-based employee compensation expense determined under fair value 2013based method for allawards net of tax [a] -50 ( 50 ) pro forma net income $ 989 earnings per share 2013 basic as reported $ 3.89 earnings per share 2013 basic pro forma $ 3.75 earnings per share 2013 diluted as reported $ 3.85 earnings per share 2013 diluted pro forma $ 3.71

[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 price of our common stock increased at least 20% ( 20 % ) from the price at the time of the reload grant . during the year ended december 31 , 2005 , reload option grants represented $ 19 million of the pro forma expense noted above . there were no reload option grants during 2007 and 2006 as stock options exercised after january 1 , 2006 are not eligible for the reload feature . earnings per share 2013 basic earnings per share are calculated on the weighted-average number of common shares outstanding during each period . diluted earnings per share include shares issuable upon exercise of outstanding stock options and stock-based awards where the conversion of such instruments would be dilutive . use of estimates 2013 our consolidated financial statements include estimates and assumptions regarding certain assets , liabilities , revenue , and expenses and the disclosure of certain contingent assets and liabilities . actual future results may differ from such estimates . income taxes 2013 as required under fasb statement no . 109 , accounting for income taxes , we account for income taxes by recording taxes payable or refundable for the current year and deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in our financial statements or tax returns . these expected future tax consequences are measured based on provisions of tax law as currently enacted ; the effects of future changes in tax laws are not anticipated . future tax law changes , such as a change in the corporate tax rate , could have a material impact on our financial condition or results of operations . when appropriate , we record a valuation allowance against deferred tax assets to offset future tax benefits that may not be realized . in determining whether a valuation allowance is appropriate , we consider whether it is more likely than not that all or some portion of our deferred tax assets will not be realized , based on management 2019s judgments regarding the best available evidence about future events . when we have claimed tax benefits that may be challenged by a tax authority , these uncertain tax positions are accounted for under fasb interpretation no . 48 , accounting for uncertainty in income taxes , an interpretation of fasb statement no . 109 ( fin 48 ) . we adopted fin 48 beginning january 1 , 2007 . prior to 2007 , income tax contingencies were accounted for under fasb statement no . 5 , accounting for contingencies . under fin 48 , we recognize tax benefits only for tax positions that are more likely than not to be sustained upon examination by tax authorities . the amount recognized is measured as the largest amount of benefit that is greater than 50 percent likely to be realized upon settlement . a liability for 201cunrecognized tax benefits 201d is .

Question: what was the percentage difference between earnings per share 2013 diluted as reported and earnings per share 2013 diluted pro forma ?
Answer: -4%
Calculation: divide(subtract(3.71, 3.85), 3.85)