during 2009 , the company extended the contractual life of 4 million fully vested share options held by 6 employees .as a result of that modification , the company recognized additional compensation expense of $ 1 million for the year ended december 31 , 2009 .restricted stock units ( 201crsus 201d ) performance-based rsus .the company grants performance-based rsus to the company 2019s executive officers and certain employees once per year .the company may also grant performance-based rsus to certain new employees or to employees who assume positions of increasing responsibility at the time those events occur .the number of performance-based rsus that ultimately vest is dependent on one or both of the following as per the terms of the specific award agreement : the achievement of 1 ) internal profitability targets ( performance condition ) and 2 ) market performance targets measured by the comparison of the company 2019s stock performance versus a defined peer group ( market condition ) .the performance-based rsus generally cliff-vest during the company 2019s quarter-end september 30 black-out period three years from the date of grant .the ultimate number of shares of the company 2019s series a common stock issued will range from zero to stretch , with stretch defined individually under each award , net of personal income taxes withheld .the market condition is factored into the estimated fair value per unit and compensation expense for each award will be based on the probability of achieving internal profitability targets , as applicable , and recognized on a straight-line basis over the term of the respective grant , less estimated forfeitures .for performance-based rsus granted without a performance condition , compensation expense is based on the fair value per unit recognized on a straight-line basis over the term of the grant , less estimated forfeitures .in april 2007 , the company granted performance-based rsus to certain employees that vest annually in equal tranches beginning october 1 , 2008 through october 1 , 2011 and include a market condition .the performance- based rsus awarded include a catch-up provision that provides for an additional year of vesting of previously unvested amounts , subject to certain maximums .compensation expense is based on the fair value per unit recognized on a straight-line basis over the term of the grant , less estimated forfeitures .a summary of changes in performance-based rsus outstanding is as follows : number of weighted average fair value ( in thousands ) ( in $ ) .
[['', 'number of units ( in thousands )', 'weighted average fair value ( in $ )'], ['nonvested at december 31 2008', '1188', '19.65'], ['granted', '420', '38.16'], ['vested', '-79 ( 79 )', '21.30'], ['forfeited', '-114 ( 114 )', '17.28'], ['nonvested at december 31 2009', '1415', '25.24']]
the fair value of shares vested for performance-based rsus during the years ended december 31 , 2009 and 2008 was $ 2 million and $ 3 million , respectively .there were no vestings that occurred during the year ended december 31 , 2007 .fair value for the company 2019s performance-based rsus was estimated at the grant date using a monte carlo simulation approach .monte carlo simulation was utilized to randomly generate future stock returns for the company and each company in the defined peer group for each grant based on company-specific dividend yields , volatilities and stock return correlations .these returns were used to calculate future performance-based rsu vesting percentages and the simulated values of the vested performance-based rsus were then discounted to present value using a risk-free rate , yielding the expected value of these performance-based rsus .%%transmsg*** transmitting job : d70731 pcn : 119000000 ***%%pcmsg|119 |00016|yes|no|02/10/2010 16:17|0|0|page is valid , no graphics -- color : n| .

Question: what is the net change in the balance of non vested units during 2009?
Answer: 227