Iron Law of Wages

From Hobson's Choice

Term coined by Ferdinand Lasalle (d.1864) for the idea, then widespread among classical economists that humans reproduce to exhaust their means of subsistence; hence, if wages are increased, workers will have more children, who will enter the labor force, and drive wages back down. This idea is very old; it was mentioned by Richard Cantillon in his Essai sur la nature du commerce en general (1755), and it was probably commonplace by then:

Men multiply like mice in a barn if they have unlimited means of subsistence; and the English in the colonies will become more numerous in proportion in three generations than they would be in thirty in England, because in the colonies they find for cultivation new tracts of land from which they drive the savages.
[Essai, XV]

Cantillon and those who cited the "Iron Law" have typically done so as an argument against any measure taken to ease the misery of the poor.