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marathon oil corporation notes to consolidated financial statements stock appreciation rights 2013 prior to 2005, we granted sars under the 2003 plan. no stock appreciation rights have been granted under the 2007 plan. similar to stock options, stock appreciation rights represent the right to receive a payment equal to the excess of the fair market value of shares of common stock on the date the right is exercised over the grant price. under the 2003 plan, certain sars were granted as stock-settled sars and others were granted in tandem with stock options. in general, sars granted under the 2003 plan vest ratably over a three-year period and have a maximum term of ten years from the date they are granted. stock-based performance awards 2013 prior to 2005, we granted stock-based performance awards under the 2003 plan. no stock-based performance awards have been granted under the 2007 plan. beginning in 2005, we discontinued granting stock-based performance awards and instead now grant cash-settled performance units to officers. all stock-based performance awards granted under the 2003 plan have either vested or been forfeited. as a result, there are no outstanding stock-based performance awards. restricted stock 2013 we grant restricted stock and restricted stock units under the 2007 plan and previously granted such awards under the 2003 plan. in 2005, the compensation committee began granting time-based restricted stock to certain u.s.-based officers of marathon and its consolidated subsidiaries as part of their annual long-term incentive package. the restricted stock awards to officers vest three years from the date of grant, contingent on the recipient 2019s continued employment. we also grant restricted stock to certain non-officer employees and restricted stock units to certain international employees (201crestricted stock awards 201d), based on their performance within certain guidelines and for retention purposes. the restricted stock awards to non-officers generally vest in one-third increments over a three-year period, contingent on the recipient 2019s continued employment, however, certain restricted stock awards granted in 2008 will vest over a four-year period, contingent on the recipient 2019s continued employment. prior to vesting, all restricted stock recipients have the right to vote such stock and receive dividends thereon. the non-vested shares are not transferable and are held by our transfer agent. common stock units 2013 we maintain an equity compensation program for our non-employee directors under the 2007 plan and previously maintained such a program under the 2003 plan. all non-employee directors other than the chairman receive annual grants of common stock units, and they are required to hold those units until they leave the board of directors. when dividends are paid on marathon common stock, directors receive dividend equivalents in the form of additional common stock units. total stock-based compensation expense total employee stock-based compensation expense was $43 million, $66 million and $78 million in 2008, 2007 and 2006. the total related income tax benefits were $16 million, $24 million and $29 million. in 2008 and 2007, cash received upon exercise of stock option awards was $9 million and $27 million. tax benefits realized for deductions during 2008 and 2007 that were in excess of the stock-based compensation expense recorded for options exercised and other stock-based awards vested during the period totaled $7 million and $30 million. cash settlements of stock option awards totaled $1 million in 2007. there were no cash settlements in 2008. stock option awards during 2008, 2007 and 2006, we granted stock option awards to both officer and non-officer employees. the weighted average grant date fair value of these awards was based on the following black-scholes assumptions:.
|  | 2008 | 2007 | 2006 |
| --------- | --------- | --------- | --------- |
| Weighted average exercise price per share | $51.74 | $60.94 | $37.84 |
| Expected annual dividends per share | $0.96 | $0.96 | $0.80 |
| Expected life in years | 4.8 | 5.0 | 5.1 |
| Expected volatility | 30% | 27% | 28% |
| Risk-free interest rate | 3.1% | 4.1% | 5.0% |
| Weighted average grant date fair value of stock option awards granted | $13.03 | $17.24 | $10.19 |
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Please compute the result.
what was the difference in the weighted average exercise price per share between 2006 and 2008?
assistant
13.9
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and the specific value of 2006?
assistant
37.84
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and the percentage change during this time?
assistant
0.36734