humana inc .notes to consolidated financial statements 2014 ( continued ) the total intrinsic value of stock options exercised during 2007 was $ 133.9 million , compared with $ 133.7 million during 2006 and $ 57.8 million during 2005 .cash received from stock option exercises for the years ended december 31 , 2007 , 2006 , and 2005 totaled $ 62.7 million , $ 49.2 million , and $ 36.4 million , respectively .total compensation expense related to nonvested options not yet recognized was $ 23.6 million at december 31 , 2007 .we expect to recognize this compensation expense over a weighted average period of approximately 1.6 years .restricted stock awards restricted stock awards are granted with a fair value equal to the market price of our common stock on the date of grant .compensation expense is recorded straight-line over the vesting period , generally three years from the date of grant .the weighted average grant date fair value of our restricted stock awards was $ 63.59 , $ 54.36 , and $ 32.81 for the years ended december 31 , 2007 , 2006 , and 2005 , respectively .activity for our restricted stock awards was as follows for the year ended december 31 , 2007 : shares weighted average grant-date fair value .                                                | shares           | weighted average grant-date fair value
nonvested restricted stock at december 31 2006 | 1107455          | $ 45.86                               
granted                                        | 852353           | 63.59                                 
vested                                         | -51206 ( 51206 ) | 56.93                                 
forfeited                                      | -63624 ( 63624 ) | 49.65                                 
nonvested restricted stock at december 31 2007 | 1844978          | $ 53.61                                the fair value of shares vested during the years ended december 31 , 2007 , 2006 , and 2005 was $ 3.4 million , $ 2.3 million , and $ 0.6 million , respectively .total compensation expense related to nonvested restricted stock awards not yet recognized was $ 44.7 million at december 31 , 2007 .we expect to recognize this compensation expense over a weighted average period of approximately 1.4 years .there are no other contractual terms covering restricted stock awards once vested. .
Question: what was the net change in the weighted average grant-date fair value from 2006 to 2007?

Read the following texts and table with financial data from an S&P 500 earnings report carefully.Based on the question-answer history (if provided), answer the last question. The answer may require mathematical calculation based on the data provided.
humana inc .notes to consolidated financial statements 2014 ( continued ) the total intrinsic value of stock options exercised during 2007 was $ 133.9 million , compared with $ 133.7 million during 2006 and $ 57.8 million during 2005 .cash received from stock option exercises for the years ended december 31 , 2007 , 2006 , and 2005 totaled $ 62.7 million , $ 49.2 million , and $ 36.4 million , respectively .total compensation expense related to nonvested options not yet recognized was $ 23.6 million at december 31 , 2007 .we expect to recognize this compensation expense over a weighted average period of approximately 1.6 years .restricted stock awards restricted stock awards are granted with a fair value equal to the market price of our common stock on the date of grant .compensation expense is recorded straight-line over the vesting period , generally three years from the date of grant .the weighted average grant date fair value of our restricted stock awards was $ 63.59 , $ 54.36 , and $ 32.81 for the years ended december 31 , 2007 , 2006 , and 2005 , respectively .activity for our restricted stock awards was as follows for the year ended december 31 , 2007 : shares weighted average grant-date fair value .                                                | shares           | weighted average grant-date fair value
nonvested restricted stock at december 31 2006 | 1107455          | $ 45.86                               
granted                                        | 852353           | 63.59                                 
vested                                         | -51206 ( 51206 ) | 56.93                                 
forfeited                                      | -63624 ( 63624 ) | 49.65                                 
nonvested restricted stock at december 31 2007 | 1844978          | $ 53.61                                the fair value of shares vested during the years ended december 31 , 2007 , 2006 , and 2005 was $ 3.4 million , $ 2.3 million , and $ 0.6 million , respectively .total compensation expense related to nonvested restricted stock awards not yet recognized was $ 44.7 million at december 31 , 2007 .we expect to recognize this compensation expense over a weighted average period of approximately 1.4 years .there are no other contractual terms covering restricted stock awards once vested. .
Question: what was the net change in the weighted average grant-date fair value from 2006 to 2007?
