{"pre_text": ["concentration of credit risk credit risk represents the accounting loss that would be recognized at the reporting date if counterparties failed to perform as contracted .", "the company believes the likelihood of incurring material losses due to concentration of credit risk is remote .", "the principal financial instruments subject to credit risk are as follows : cash and cash equivalents - the company maintains cash deposits with major banks , which from time to time may exceed insured limits .", "the possibility of loss related to financial condition of major banks has been deemed minimal .", "additionally , the company 2019s investment policy limits exposure to concentrations of credit risk and changes in market conditions .", "accounts receivable - a large number of customers in diverse industries and geographies , as well as the practice of establishing reasonable credit lines , limits credit risk .", "based on historical trends and experiences , the allowance for doubtful accounts is adequate to cover potential credit risk losses .", "foreign currency and interest rate contracts and derivatives - exposure to credit risk is limited by internal policies and active monitoring of counterparty risks .", "in addition , the company uses a diversified group of major international banks and financial institutions as counterparties .", "the company does not anticipate nonperformance by any of these counterparties .", "cash and cash equivalents cash equivalents include highly-liquid investments with a maturity of three months or less when purchased .", "accounts receivable and allowance for doubtful accounts accounts receivable are carried at their face amounts less an allowance for doubtful accounts .", "accounts receivable are recorded at the invoiced amount and generally do not bear interest .", "the company estimates the balance of allowance for doubtful accounts by analyzing accounts receivable balances by age and applying historical write-off and collection trend rates .", "the company 2019s estimates include separately providing for customer balances based on specific circumstances and credit conditions , and when it is deemed probable that the balance is uncollectible .", "account balances are charged off against the allowance when it is determined the receivable will not be recovered .", "the company 2019s allowance for doubtful accounts balance also includes an allowance for the expected return of products shipped and credits related to pricing or quantities shipped of $ 15 million as of december 31 , 2015 and 2014 and $ 14 million as of december 31 , 2013 .", "returns and credit activity is recorded directly to sales .", "the following table summarizes the activity in the allowance for doubtful accounts: ."], "post_text": ["( a ) other amounts are primarily the effects of changes in currency translations and the impact of allowance for returns and credits .", "inventory valuations inventories are valued at the lower of cost or market .", "certain u.s .", "inventory costs are determined on a last-in , first-out ( lifo ) basis .", "lifo inventories represented 39% ( 39 % ) and 37% ( 37 % ) of consolidated inventories as of december 31 , 2015 and 2014 , respectively .", "lifo inventories include certain legacy nalco u.s .", "inventory acquired at fair value as part of the nalco merger .", "all other inventory costs are determined using either the average cost or first-in , first-out ( fifo ) methods .", "inventory values at fifo , as shown in note 5 , approximate replacement during the fourth quarter of 2015 , the company improved estimates related to its inventory reserves and product costing , resulting in a net pre-tax charge of approximately $ 6 million .", "separately , the actions resulted in charge of $ 20.6 million related to inventory reserve calculations , partially offset by a gain of $ 14.5 million related to the capitalization of certain cost components into inventory .", "both of these items are reflected in note 3. ."], "table": [["( millions )", "2015", "2014", "2013"], ["beginning balance", "$ 77", "$ 81", "$ 73"], ["bad debt expense", "26", "23", "28"], ["write-offs", "-22 ( 22 )", "-20 ( 20 )", "-21 ( 21 )"], ["other ( a )", "-6 ( 6 )", "-7 ( 7 )", "1"], ["ending balance", "$ 75", "$ 77", "$ 81"]], "table_ori": [["(millions)", "2015", "2014", "2013"], ["Beginning balance", "$77", "$81", "$73"], ["Bad debt expense", "26", "23", "28"], ["Write-offs", "(22)", "(20)", "(21)"], ["Other (a)", "(6)", "(7)", "1"], ["Ending balance", "$75", "$77", "$81"]]}

Question: what is the net change in the balance of allowance for doubtful accounts during 2015?
Evidence:
table_2: ( millions ) the bad debt expense of 2015 is 26 ; the bad debt expense of 2014 is 23 ; the bad debt expense of 2013 is 28 ;
table_3: ( millions ) the write-offs of 2015 is -22 ( 22 ) ; the write-offs of 2014 is -20 ( 20 ) ; the write-offs of 2013 is -21 ( 21 ) ;
table_4: ( millions ) the other ( a ) of 2015 is -6 ( 6 ) ; the other ( a ) of 2014 is -7 ( 7 ) ; the other ( a ) of 2013 is 1 ;
Program: add(26, -22), add(#0, -6)
Answer:
str_answer: -2
exe_answer: -2