I've seen some figures for "war materiel" produced
per year by the major actors in World War II.
Here's the quotes (from rec.arts.sf.written, by
aspqrz at sydney.DIALix.oz.au (Phillip McGregor),
9 Nov 1995):
<quote>
Approx Spending on Armaments (1994 US$, Billions)
1939 1940 1941 1942 1943 1944
US 5.4 13.5 40.5 180 342 379 UK 9 31.5 58.5 81 99 100 Canada 0 0 4.5 9 13.5 13.5 USSR 30 45 76 104 125 144
Germany 31 54 54 77 124 153 Japan 4.5 9 18 27 42 54 <end quote>
The two enconomies weren't comparable--the US was capable
of outproducing Germany by two or three to one. The Axis'
only hope was to win a quick war and reach a settlement
before the US got its act in gear.
So 10% or 50% extra production in Germany wouldn't have
made more of a difference than a slight rescheduling of
Germany's defeat--though if it's postponed more than a
month or so, the A-bomb would be ready to be used on
Germany, so the defeat can't be prolonged much past August
(Hiroshima drop was August 6, 1945 if I've got it right).
Either way they lose in the summer of 1945.