The Art of War by Sun Tzu

II Waging War

13 & 14 With this loss of substance and exhaustion of strength, the homes of the people will be stripped bare, and three tenths of their income will be dissipated; while government expenses for broken chariots, worn out horses, breast plates and helmets, bows and arrows, spears and shields, protective mantles, draught oxen and heavy wagons, will amount to four-tenths of its total revenue.

Notes by Zephyrist:

We were talking about the proximity of an army which causes prices to go up and this in turn causes the people's substance to be drained away.

Sun Tzu is talking about basic economics, demand increases whilst supply stays the same so prices rise. Peasant incomes don't increase so 30% of their income just vanishes as it is used to pay for the price rise in food.

The second part is that a standing army will cause defence spending to rise to 40% of the government's revenue.

How applicable these figures are in today's economic climate is debatable and perhaps the figures Sun Tzu quotes are too vague to analyse