{"pre_text": ["american tower corporation and subsidiaries notes to consolidated financial statements when they are determined uncollectible .", "such determination includes analysis and consideration of the particular conditions of the account .", "changes in the allowances were as follows for the years ended december 31 , ( in thousands ) : ."], "post_text": ["functional currency 2014as a result of changes to the organizational structure of the company 2019s subsidiaries in latin america in 2010 , the company determined that effective january 1 , 2010 , the functional currency of its foreign subsidiary in brazil is the brazilian real .", "from that point forward , all assets and liabilities held by the subsidiary in brazil are translated into u.s .", "dollars at the exchange rate in effect at the end of the applicable reporting period .", "revenues and expenses are translated at the average monthly exchange rates and the cumulative translation effect is included in equity .", "the change in functional currency from u.s .", "dollars to brazilian real gave rise to an increase in the net value of certain non-monetary assets and liabilities .", "the aggregate impact on such assets and liabilities was $ 39.8 million with an offsetting increase in accumulated other comprehensive income during the year ended december 31 , 2010 .", "as a result of the renegotiation of the company 2019s agreements with grupo iusacell , s.a .", "de c.v .", "( 201ciusacell 201d ) , which included , among other changes , converting iusacell 2019s contractual obligations to the company from u.s .", "dollars to mexican pesos , the company determined that effective april 1 , 2010 , the functional currency of certain of its foreign subsidiaries in mexico is the mexican peso .", "from that point forward , all assets and liabilities held by those subsidiaries in mexico are translated into u.s .", "dollars at the exchange rate in effect at the end of the applicable reporting period .", "revenues and expenses are translated at the average monthly exchange rates and the cumulative translation effect is included in equity .", "the change in functional currency from u.s .", "dollars to mexican pesos gave rise to a decrease in the net value of certain non-monetary assets and liabilities .", "the aggregate impact on such assets and liabilities was $ 33.6 million with an offsetting decrease in accumulated other comprehensive income .", "the functional currency of the company 2019s other foreign operating subsidiaries is also the respective local currency .", "all assets and liabilities held by the subsidiaries are translated into u.s .", "dollars at the exchange rate in effect at the end of the applicable fiscal reporting period .", "revenues and expenses are translated at the average monthly exchange rates .", "the cumulative translation effect is included in equity as a component of accumulated other comprehensive income .", "foreign currency transaction gains and losses are recognized in the consolidated statements of operations and are the result of transactions of a subsidiary being denominated in a currency other than its functional currency .", "cash and cash equivalents 2014cash and cash equivalents include cash on hand , demand deposits and short-term investments , including money market funds , with remaining maturities of three months or less when acquired , whose cost approximates fair value .", "restricted cash 2014the company classifies as restricted cash all cash pledged as collateral to secure obligations and all cash whose use is otherwise limited by contractual provisions , including cash on deposit in reserve accounts relating to the commercial mortgage pass-through certificates , series 2007-1 issued in the company 2019s securitization transaction and the secured cellular site revenue notes , series 2010-1 class c , series 2010-2 class c and series 2010-2 class f , assumed by the company as a result of the acquisition of certain legal entities from unison holdings , llc and unison site management ii , l.l.c .", "( collectively , 201cunison 201d ) . ."], "table": [["", "2012", "2011", "2010"], ["balance as of january 1", "$ 24412", "$ 22505", "$ 28520"], ["current year increases", "8028", "17008", "16219"], ["write-offs net of recoveries and other", "-12034 ( 12034 )", "-15101 ( 15101 )", "-22234 ( 22234 )"], ["balance as of december 31", "$ 20406", "$ 24412", "$ 22505"]], "table_ori": [["", "2012", "2011", "2010"], ["Balance as of January 1", "$24,412", "$22,505", "$28,520"], ["Current year increases", "8,028", "17,008", "16,219"], ["Write-offs, net of recoveries and other", "(12,034)", "(15,101)", "(22,234)"], ["Balance as of December 31", "$20,406", "$24,412", "$22,505"]]}

Question: what was the average bad debt allowance for the past three years , in billions?
Evidence:
table_4: the balance as of december 31 of 2012 is $ 20406 ; the balance as of december 31 of 2011 is $ 24412 ; the balance as of december 31 of 2010 is $ 22505 ;
Program: table_average(balance as of december 31, none)
Answer:
str_answer: 22441
exe_answer: 22441