pre_text: aeronautics our aeronautics business segment is engaged in the research , design , development , manufacture , integration , sustainment , support , and upgrade of advanced military aircraft , including combat and air mobility aircraft , unmanned air vehicles , and related technologies . aeronautics 2019 major programs include the f-35 lightning ii joint strike fighter , c-130 hercules , f-16 fighting falcon , f-22 raptor , and the c-5m super galaxy . aeronautics 2019 operating results included the following ( in millions ) : .
post_text: 2013 compared to 2012 aeronautics 2019 net sales for 2013 decreased $ 830 million , or 6% ( 6 % ) , compared to 2012 . the decrease was primarily attributable to lower net sales of approximately $ 530 million for the f-16 program due to fewer aircraft deliveries ( 13 aircraft delivered in 2013 compared to 37 delivered in 2012 ) partially offset by aircraft configuration mix ; about $ 385 million for the c-130 program due to fewer aircraft deliveries ( 25 aircraft delivered in 2013 compared to 34 in 2012 ) partially offset by increased sustainment activities ; approximately $ 255 million for the f-22 program , which includes about $ 205 million due to decreased production volume as final aircraft deliveries were completed during the second quarter of 2012 and $ 50 million from the favorable resolution of a contractual matter during the second quarter of 2012 ; and about $ 270 million for various other programs ( primarily sustainment activities ) due to decreased volume . the decreases were partially offset by higher net sales of about $ 295 million for f-35 production contracts due to increased production volume and risk retirements ; approximately $ 245 million for the c-5 program due to increased aircraft deliveries ( six aircraft delivered in 2013 compared to four in 2012 ) and other modernization activities ; and about $ 70 million for the f-35 development contract due to increased volume . aeronautics 2019 operating profit for 2013 decreased $ 87 million , or 5% ( 5 % ) , compared to 2012 . the decrease was primarily attributable to lower operating profit of about $ 85 million for the f-22 program , which includes approximately $ 50 million from the favorable resolution of a contractual matter in the second quarter of 2012 and about $ 35 million due to decreased risk retirements and production volume ; approximately $ 70 million for the c-130 program due to lower risk retirements and fewer deliveries partially offset by increased sustainment activities ; about $ 65 million for the c-5 program due to the inception-to-date effect of reducing the profit booking rate in the third quarter of 2013 and lower risk retirements ; approximately $ 35 million for the f-16 program due to fewer aircraft deliveries partially offset by increased sustainment activity and aircraft configuration mix . the decreases were partially offset by higher operating profit of approximately $ 180 million for f-35 production contracts due to increased risk retirements and volume . operating profit was comparable for the f-35 development contract and included adjustments of approximately $ 85 million to reflect the inception-to-date impacts of the downward revisions to the profit booking rate in both 2013 and 2012 . adjustments not related to volume , including net profit booking rate adjustments and other matters , were approximately $ 75 million lower for 2013 compared to 2012 compared to 2011 aeronautics 2019 net sales for 2012 increased $ 591 million , or 4% ( 4 % ) , compared to 2011 . the increase was attributable to higher net sales of approximately $ 745 million from f-35 production contracts principally due to increased production volume ; about $ 285 million from f-16 programs primarily due to higher aircraft deliveries ( 37 f-16 aircraft delivered in 2012 compared to 22 in 2011 ) partially offset by lower volume on sustainment activities due to the completion of modification programs for certain international customers ; and approximately $ 140 million from c-5 programs due to higher aircraft deliveries ( four c-5m aircraft delivered in 2012 compared to two in 2011 ) . partially offsetting the increases were lower net sales of approximately $ 365 million from decreased production volume and lower risk retirements on the f-22 program as final aircraft deliveries were completed in the second quarter of 2012 ; approximately $ 110 million from the f-35 development contract primarily due to the inception-to-date effect of reducing the profit booking rate in the second quarter of 2012 and to a lesser extent lower volume ; and about $ 95 million from a decrease in volume on other sustainment activities partially offset by various other aeronautics programs due to higher volume . net sales for c-130 programs were comparable to 2011 as a decline in sustainment activities largely was offset by increased aircraft deliveries. .
table: 2013 2012 2011
table: Net sales $14,123 $14,953 $14,362
table: Operating profit 1,612 1,699 1,630
table: Operating margins 11.4% 11.4% 11.3%
table: Backlog at year-end 28,000 30,100 30,500
question: Analyse this data from a financial earnings document. what was the average net sales from 2011 to 2013