The Wealth of Nations by Part 1 Chapter 7 Page 11

suits itself in this manner to the effectual demand. It naturally aims at bringing always that precise quantity thither which may be sufficient to supply, and no more than supply, that demand.

But in some employments the same quantity of industry will in different years produce very different quantities of commodities; while in others it will produce always the same, or very nearly the same. The same number of labourers in husbandry will, in different years, produce very different quantities of corn, wine, oil, hops, etc. But the same number of spinners and weavers will every year produce the same or very nearly the same quantity of linen and woollen cloth. It is only the average produce of the one species of industry which can be suited in any respect to the effectual demand; and as its actual produce is frequently much