Please answer the given financial question based on the context.
Context: 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 is the increase observed in the weighted average grant date fair value of the restricted stocks in 2006 and 2007?


Answer: The answer is:0.16979