The Wealth of Nations by Part 1 Chapter 7 Page 14

A rent which consists either in a certain proportion or in a certain quantity of the rude produce, is no doubt affected in its yearly value by all the occasional and temporary fluctuations in the market price of that rude produce; but it is seldom affected by them in its yearly rate.

In settling the terms of the lease, the landlord and farmer endeavour, according to their best judgment, to adjust that rate, not to the temporary and occasional, but to the average and ordinary price of the produce.

Such fluctuations affect both the value and the rate either of wages or of profit, according as the market happens to be either overstocked or understocked with commodities or with labour; with work done, or with work to be done. A public mourning raises the price of black cloth (with which