In order to calculate the size of the cake which will be left for civilian consumption, we have to estimate (1) the maximum current output that we are capable of organising from our resources of men and plant and materials, (2) how fast we can safely draw on our foreign reserves by importing more than we export, (3) how much of all this will be used up by our war effort.

Ch. 3 : Our Output Capacity and the National Income - How to Pay for the War (1940)