marathon oil corporation notes to consolidated financial statements restricted stock awards the following is a summary of restricted stock award activity . awards weighted-average grant date fair value .
according to the above listed weighted average grant date fair value , by what percentage did the value of unvested restricted stock awards decrease from 2008 to 2009?
the vesting date fair value of restricted stock awards which vested during 2009 , 2008 and 2007 was $ 24 million , $ 38 million and $ 29 million . the weighted average grant date fair value of restricted stock awards was $ 44.89 , $ 47.72 , and $ 39.87 for awards unvested at december 31 , 2009 , 2008 and 2007 . as of december 31 , 2009 , there was $ 43 million of unrecognized compensation cost related to restricted stock awards which is expected to be recognized over a weighted average period of 1.6 years . stock-based performance awards all stock-based performance awards have either vested or been forfeited . the vesting date fair value of stock- based performance awards which vested during 2007 was $ 38 . 24 . stockholders 2019 equity in each year , 2009 and 2008 , we issued 2 million in common stock upon the redemption of the exchangeable shares described below in addition to treasury shares issued for employee stock-based awards . the board of directors has authorized the repurchase of up to $ 5 billion of marathon common stock . purchases under the program may be in either open market transactions , including block purchases , or in privately negotiated transactions . we will use cash on hand , cash generated from operations , proceeds from potential asset sales or cash from available borrowings to acquire shares . this program may be changed based upon our financial condition or changes in market conditions and is subject to termination prior to completion . the repurchase program does not include specific price targets or timetables . as of december 31 , 2009 , we have acquired 66 million common shares at a cost of $ 2922 million under the program . no shares have been acquired since august 2008 . securities exchangeable into marathon common stock 2013 as discussed in note 6 , we acquired all of the outstanding shares of western on october 18 , 2007 . the western shareholders who were canadian residents received , at their election , cash , marathon common stock , securities exchangeable into marathon common stock ( the 201cexchangeable shares 201d ) or a combination thereof . the western shareholders elected to receive 5 million exchangeable shares as part of the acquisition consideration . the exchangeable shares are shares of an indirect canadian subsidiary of marathon and , at the acquisition date , were exchangeable on a one-for-one basis into marathon common stock . subsequent to the acquisition , the exchange ratio is adjusted to reflect cash dividends , if any , paid on marathon common stock and cash dividends , if any , paid on the exchangeable shares . the exchange ratio at december 31 , 2009 , was 1.06109 common shares for each exchangeable share . the exchangeable shares are exchangeable at the option of the holder at any time and are automatically redeemable on october 18 , 2011 . holders of exchangeable shares are entitled to instruct a trustee to vote ( or obtain a proxy from the trustee to vote directly ) on all matters submitted to the holders of marathon common stock . the number of votes to which each holder is entitled is equal to the whole number of shares of marathon common stock into which such holder 2019s exchangeable shares would be exchangeable based on the exchange ratio in effect on the record date for the vote . the voting right is attached to voting preferred shares of marathon that were issued to a trustee in an amount .