{"pre_text": ["the performance units granted to certain executives in fiscal 2014 were based on a one-year performance period .", "after the compensation committee certified the performance results , 25% ( 25 % ) of the performance units converted to unrestricted shares .", "the remaining 75% ( 75 % ) converted to restricted shares that vest in equal installments on each of the first three anniversaries of the conversion date .", "the performance units granted to certain executives during fiscal 2015 were based on a three-year performance period .", "after the compensation committee certifies the performance results for the three-year period , performance units earned will convert into unrestricted common stock .", "the compensation committee may set a range of possible performance-based outcomes for performance units .", "depending on the achievement of the performance measures , the grantee may earn up to 200% ( 200 % ) of the target number of shares .", "for awards with only performance conditions , we recognize compensation expense over the performance period using the grant date fair value of the award , which is based on the number of shares expected to be earned according to the level of achievement of performance goals .", "if the number of shares expected to be earned were to change at any time during the performance period , we would make a cumulative adjustment to share-based compensation expense based on the revised number of shares expected to be earned .", "during fiscal 2015 , certain executives were granted performance units that we refer to as leveraged performance units , or lpus .", "lpus contain a market condition based on our relative stock price growth over a three-year performance period .", "the lpus contain a minimum threshold performance which , if not met , would result in no payout .", "the lpus also contain a maximum award opportunity set as a fixed dollar and fixed number of shares .", "after the three-year performance period , one-third of any earned units converts to unrestricted common stock .", "the remaining two-thirds convert to restricted stock that will vest in equal installments on each of the first two anniversaries of the conversion date .", "we recognize share-based compensation expense based on the grant date fair value of the lpus , as determined by use of a monte carlo model , on a straight-line basis over the requisite service period for each separately vesting portion of the lpu award .", "total shareholder return units before fiscal 2015 , certain of our executives were granted total shareholder return ( 201ctsr 201d ) units , which are performance-based restricted stock units that are earned based on our total shareholder return over a three-year performance period compared to companies in the s&p 500 .", "once the performance results are certified , tsr units convert into unrestricted common stock .", "depending on our performance , the grantee may earn up to 200% ( 200 % ) of the target number of shares .", "the target number of tsr units for each executive is set by the compensation committee .", "we recognize share-based compensation expense based on the grant date fair value of the tsr units , as determined by use of a monte carlo model , on a straight-line basis over the vesting period .", "the following table summarizes the changes in unvested share-based awards for the years ended may 31 , 2015 and 2014 ( shares in thousands ) : shares weighted-average grant-date fair value ."], "post_text": ["global payments inc .", "| 2015 form 10-k annual report 2013 81 ."], "table": [["", "shares", "weighted-averagegrant-datefair value"], ["unvested at may 31 2013", "1096", "$ 44"], ["granted", "544", "47"], ["vested", "-643 ( 643 )", "45"], ["forfeited", "-120 ( 120 )", "45"], ["unvested at may 31 2014", "877", "45"], ["granted", "477", "72"], ["vested", "-324 ( 324 )", "46"], ["forfeited", "-106 ( 106 )", "53"], ["unvested at may 31 2015", "924", "$ 58"]], "table_ori": [["", "Shares", "Weighted-AverageGrant-DateFair Value"], ["Unvested at May 31, 2013", "1,096", "$44"], ["Granted", "544", "47"], ["Vested", "(643)", "45"], ["Forfeited", "(120)", "45"], ["Unvested at May 31, 2014", "877", "45"], ["Granted", "477", "72"], ["Vested", "(324)", "46"], ["Forfeited", "(106)", "53"], ["Unvested at May 31, 2015", "924", "$58"]]}

Question: what is the net change in the balance of unvested shares from 2013 to 2015?
Evidence:
table_1: the unvested at may 31 2013 of shares is 1096 ; the unvested at may 31 2013 of weighted-averagegrant-datefair value is $ 44 ;
table_9: the unvested at may 31 2015 of shares is 924 ; the unvested at may 31 2015 of weighted-averagegrant-datefair value is $ 58 ;
Program: subtract(924, 1096)
Answer:
str_answer: -172
exe_answer: -172