From Tooze's Arming the Reich:
> the pace of expansion in the Army’s output was not maintained beyond the summer of 1940. The overall output of the sector continued to rise, but at a slower pace and it was subject to considerable fluctuations. But what actually lies behind this break in the armaments curve is a spetacular divergence between the production of weapons, vehicles and tanks which continued to rise and the production of ammunition which dropped away precipitately in the second half of 1940. This striking discontinuity which is crucial in depressing the overall armaments index, clearly cannot be explained in terms of generic inefficiency affecting the entirety of the armaments economy, as suggested by Overy and Mueller. It was in fact the result of a deliberate decision to scale back ammunition production.
> There can be no doubt of course that interrupting the upsurge in ammunition production in this abrupt fashion was not conducive to maximizing shop-floor efficiency. However, to have sustained the enormous rate of ammunition production in the summer of 1940, without regard to military necessity would have been entirely irrational. From the summer of 1940 onwards, the record of German armaments production bears the hallmarks not of chronic inefficiency as Overy and Mueller argue, but of a deliberate balancing act.
> It is certainly true that as of the summer of 1940 Germany was no longer focussing all possible resources on maximizing current output of armaments, but this was not to the benefit of civilian consumption. Alongside the production of weapons, tanks and U Boats, what increased in 1940 and 1941 were exports – vital to sustaining the economies of Germany’s allies and friendly neutrals – and investment, which surged spectacularly. Both were justified as contributions towards Germany’s ability to sustain a long sea and air war against Britain and the United States.