pre_text: allowance for doubtful accounts is as follows: .
post_text: discontinued operations during the fourth quarter of 2009 , schlumberger recorded a net $ 22 million charge related to the resolution of a customs assessment pertaining to its former offshore contract drilling business , as well as the resolution of certain contingencies associated with other previously disposed of businesses . this amount is included in income ( loss ) from discontinued operations in the consolidated statement of income . during the first quarter of 2008 , schlumberger recorded a gain of $ 38 million related to the resolution of a contingency associated with a previously disposed of business . this gain is included in income ( loss ) from discon- tinued operations in the consolidated statement of income . part ii , item 8 .
table: 2010 2009 2008
table: Balance at beginning of year $160 $133 $86
table: Provision 38 54 65
table: Amounts written off (13) (27) (18)
table: Balance at end of year $185 $160 $133
question: Analyse this data from a financial earnings document. what was the percentage increase in the allowance in doubtful accounts from 2009 to 2010