The Wealth of Nations by Part 4 Chapter 5 Page 11

in the actual state of the crop. Even upon this very moderate supposition, the great body of the people, over and above contributing the tax which pays the bounty of five shillings upon every quarter of wheat exported, must pay another of four shillings upon every quarter which they themselves consume. But, according to the very well informed author of the tracts upon the corn trade, the average proportion of the corn exported to that consumed at home is not more than that of one to thirty-one.

For every five shillings, therefore, which they contribute to the payment of the first tax, they must contribute six pounds four shillings to the payment of the second. So very heavy a tax upon the first necessary of life must either reduce the subsistence of the labouring poor, or it must occasion some augmentation in their