here is a 2009 post from me at HGD: ( note this applies to when AA50 came out)
All you have to do to extrapolate these GDP numbers is to divide the GDP by 15
using 1941 numbers:
Axis: 911 divided by 15= 60.73
Allies: 1798 divided by 15= 119.86
IN AA50 the axis are at 60 total
IN AA50 the allies are at 112 total
This is why the game is somewhat accurate, and the balancing is all force projection with the advantage going to the axis, and the US and UK player facing the commitment of their forces all over the map.
For 1940 you have to make additional considerations because the game will have say 50% more territories than AA50, so the number you divide will be smaller and the total will be greater in the game so that you don’t have too many worthless territories.
So lets do June 4th, 1940:
Germany: 387, plus Poland 76.6, Czecho-Slovakia 30.3, Netherlands 44.5, Belgium 39.6, Norway 11.6, Denmark 20.9, Austria 27=637.5
Italy:147 = 9.8 IPC
Japan: 192= 12.8 IPC
US colonies: 23.9
Total: 966.9= 64.4 IPC
UK colonies 14.4
Total 330.4= 22 IPC
French colonies 10.9
Total 92.9= 6.2 IPC
Baltic states 12.9
Total 429.9= 28.6 IPC
Now you have to account for peace time status vs. total war mobilization for both USA and USSR. The amount of GDP used for wartime purposes was at least twice as great for the current belligerents than neutrals. So i would put USA and USSR at 50% rate with the difference going to domestic purposes.
So problem solved. Game balanced unless your trying to make the game unhistorical with notions that the axis had ZERO chance to win, which is a bogus argument even by economics.