. adjustments not related to volume , including net profit booking rate adjustments and other matters , were approximately $ 100 million higher in 2015 compared to 2014 . backlog backlog increased in 2016 compared to 2015 primarily due to higher orders on f-35 production and sustainment programs . backlog increased in 2015 compared to 2014 primarily due to higher orders on f-35 and c-130 programs