note 4 : property , plant and equipment the following table summarizes the major classes of property , plant and equipment by category as of december 31 : 2015 2014 range of remaining useful weighted average useful life utility plant : land and other non-depreciable assets ..........$ 141 $ 137 sources of supply ..........................705 681 12 to 127 years 51 years treatment and pumping facilities ..............3070 2969 3 to 101 years 39 years transmission and distribution facilities .........8516 7963 9 to 156 years 83 years services , meters and fire hydrants .............3250 3062 8 to 93 years 35 years general structures and equipment .............1227 1096 1 to 154 years 39 years waste treatment , pumping and disposal .........313 281 2 to 115 years 46 years waste collection ...........................473 399 5 to 109 years 56 years construction work in progress ................404 303 total utility plant ..............................18099 16891 nonutility property .............................405 378 3 to 50 years 6 years total property , plant and equipment ...............$ 18504 $ 17269 property , plant and equipment depreciation expense amounted to $ 405 , $ 392 , and $ 374 for the years ended december 31 , 2015 , 2014 and 2013 , respectively and was included in depreciation and amortization expense in the accompanying consolidated statements of operations .the provision for depreciation expressed as a percentage of the aggregate average depreciable asset balances was 3.13% ( 3.13 % ) for the year ended december 31 , 2015 and 3.20% ( 3.20 % ) for years december 31 , 2014 and 2013 .note 5 : allowance for uncollectible accounts the following table summarizes the changes in the company 2019s allowances for uncollectible accounts for the years ended december 31: .                                   | 2015         | 2014         | 2013        
balance as of january 1           | $ -35 ( 35 ) | $ -34 ( 34 ) | $ -27 ( 27 )
amounts charged to expense        | -32 ( 32 )   | -37 ( 37 )   | -27 ( 27 )  
amounts written off               | 38           | 43           | 24          
recoveries of amounts written off | -10 ( 10 )   | -7 ( 7 )     | -4 ( 4 )    
balance as of december 31         | $ -39 ( 39 ) | $ -35 ( 35 ) | $ -34 ( 34 ) .
Question: in 2013, as part of the company's noncollectable amounts, how much did those amounts written off represent in relation to the recovered ones?
Steps: divide(43, const_7)
Answer: 6.14286
Question: and from that year to 2015, what was the increase in the property, plant and equipment depreciation expense?

Read the following texts and table with financial data from an S&P 500 earnings report carefully.Based on the question-answer history (if provided), answer the last question. The answer may require mathematical calculation based on the data provided.
note 4 : property , plant and equipment the following table summarizes the major classes of property , plant and equipment by category as of december 31 : 2015 2014 range of remaining useful weighted average useful life utility plant : land and other non-depreciable assets ..........$ 141 $ 137 sources of supply ..........................705 681 12 to 127 years 51 years treatment and pumping facilities ..............3070 2969 3 to 101 years 39 years transmission and distribution facilities .........8516 7963 9 to 156 years 83 years services , meters and fire hydrants .............3250 3062 8 to 93 years 35 years general structures and equipment .............1227 1096 1 to 154 years 39 years waste treatment , pumping and disposal .........313 281 2 to 115 years 46 years waste collection ...........................473 399 5 to 109 years 56 years construction work in progress ................404 303 total utility plant ..............................18099 16891 nonutility property .............................405 378 3 to 50 years 6 years total property , plant and equipment ...............$ 18504 $ 17269 property , plant and equipment depreciation expense amounted to $ 405 , $ 392 , and $ 374 for the years ended december 31 , 2015 , 2014 and 2013 , respectively and was included in depreciation and amortization expense in the accompanying consolidated statements of operations .the provision for depreciation expressed as a percentage of the aggregate average depreciable asset balances was 3.13% ( 3.13 % ) for the year ended december 31 , 2015 and 3.20% ( 3.20 % ) for years december 31 , 2014 and 2013 .note 5 : allowance for uncollectible accounts the following table summarizes the changes in the company 2019s allowances for uncollectible accounts for the years ended december 31: .                                   | 2015         | 2014         | 2013        
balance as of january 1           | $ -35 ( 35 ) | $ -34 ( 34 ) | $ -27 ( 27 )
amounts charged to expense        | -32 ( 32 )   | -37 ( 37 )   | -27 ( 27 )  
amounts written off               | 38           | 43           | 24          
recoveries of amounts written off | -10 ( 10 )   | -7 ( 7 )     | -4 ( 4 )    
balance as of december 31         | $ -39 ( 39 ) | $ -35 ( 35 ) | $ -34 ( 34 ) .
Question: in 2013, as part of the company's noncollectable amounts, how much did those amounts written off represent in relation to the recovered ones?
Steps: divide(43, const_7)
Answer: 6.14286
Question: and from that year to 2015, what was the increase in the property, plant and equipment depreciation expense?
