. grants of restricted shares generally vest one year after the date of grant with respect to 25% ( 25 % ) of the shares granted , an additional 25% ( 25 % ) after two years , an additional 25% ( 25 % ) after three years , and the remaining 25% ( 25 % ) after four years . the following table summarizes the changes in non-vested restricted stock awards for the years ended may 31 , 2010 and 2009 ( share awards in thousands ) : shares weighted average grant-date fair value .