backlog backlog increased in 2015 compared to 2014 primarily due to higher orders on f-35 and c-130 programs .
backlog decreased slightly in 2014 compared to 2013 primarily due to lower orders on f-16 and f-22 programs .
trends we expect aeronautics 2019 2016 net sales to increase in the mid-single digit percentage range as compared to 2015 due to increased volume on the f-35 and c-130 programs , partially offset by decreased volume on the f-16 program .
operating profit is also expected to increase in the low single-digit percentage range , driven by increased volume on the f-35 program offset by contract mix that results in a slight decrease in operating margins between years .
information systems & global solutions our is&gs business segment provides advanced technology systems and expertise , integrated information technology solutions and management services across a broad spectrum of applications for civil , defense , intelligence and other government customers .
is&gs 2019 technical services business provides a comprehensive portfolio of technical and sustainment services .
is&gs has a portfolio of many smaller contracts as compared to our other business segments .
is&gs has been impacted by the continued downturn in certain federal agencies 2019 information technology budgets and increased re-competition on existing contracts coupled with the fragmentation of large contracts into multiple smaller contracts that are awarded primarily on the basis of price .
is&gs 2019 operating results included the following ( in millions ) : .

2015
2014
2013
Net sales
$5,596
$5,654
$6,115
Operating profit
508
472
498
Operating margins
9.1%
8.3%
8.1%
Backlog at year-end
$4,800
$6,000
$6,300

2015 compared to 2014 is&gs 2019 net sales decreased $ 58 million , or 1% ( 1 % ) , in 2015 as compared to 2014 .
the decrease was attributable to lower net sales of approximately $ 395 million as a result of key program completions , lower customer funding levels and increased competition , coupled with the fragmentation of existing large contracts into multiple smaller contracts that are awarded primarily on the basis of price when re-competed ( including cms-citic ) .
these decreases were partially offset by higher net sales of approximately $ 230 million for businesses acquired in 2014 ; and approximately $ 110 million due to the start-up of new programs and growth in recently awarded programs .
is&gs 2019 operating profit increased $ 36 million , or 8% ( 8 % ) , in 2015 as compared to 2014 .
the increase was attributable to improved program performance and risk retirements , offset by decreased operating profit resulting from the activities mentioned above for net sales .
adjustments not related to volume , including net profit booking rate adjustments and other matters , were approximately $ 70 million higher in 2015 compared to 2014 .
2014 compared to 2013 is&gs 2019 net sales decreased $ 461 million , or 8% ( 8 % ) , in 2014 as compared to 2013 .
the decrease was primarily attributable to lower net sales of about $ 475 million due to the wind-down or completion of certain programs , driven by reductions in direct warfighter support ( including jieddo ) ; and approximately $ 320 million due to decreased volume in technical services programs reflecting market pressures .
the decreases were offset by higher net sales of about $ 330 million due to the start-up of new programs , growth in recently awarded programs and integration of recently acquired companies .
is&gs 2019 operating profit decreased $ 26 million , or 5% ( 5 % ) , in 2014 as compared to 2013 .
the decrease was primarily attributable to the activities mentioned above for sales , partially offset by severance recoveries related to the restructuring announced in november 2013 of approximately $ 20 million in 2014 .
adjustments not related to volume , including net profit booking rate adjustments , were comparable in 2014 and 2013. .

Question: Analyse this data from a financial earnings document. what was the average backlog at year-end from 2013 to 2015?
Choices:
5700.0
3731.7
0
10500
43.3
Correct choice index: 0