Serf's Up!: "According to [Evsey] Domar, serfdom actually withered away before the Black Death...(2003):
...as European population grew close to its Malthusian limit. The puzzle is why serfdom wasn't reinstituted after the Black Death. Domar was motivated by his knowledge of Russian history. Serfdom in Russia, he knew, wasn't an institution that dated back to the Dark Ages. Instead, it was mainly a 16th-century creation, contemporaneous with the beginning of the great Russian expansion into the steppes. Why? He came up with a simple yet powerful insight: there's no point in enslaving or enserfing a man unless the wage you would have to pay him if he was free is substantially above the cost of feeding, housing, and clothing him.
Imagine a pre-industrial society where population is pressing on limited land supplies, and the marginal product of labor - and hence the real wage rate under competitive conditions - is barely at subsistence. In that case, why bother establishing property rights in human beings? It costs no more to hire a free worker than to feed an indentured laborer. Indeed, by 1300 - with Europe very much a Malthusian society - serfdom had withered away from lack of interest.
But now suppose that for some reason land becomes abundant, and labor scarce. Then competition among landowners will tend to push up wages of free workers, and the ruling class will try, if it can, to pin peasants down and prevent them from bargaining for a higher standard of living. In Russia, it was all about gunpowder: suddenly steppe nomads were no longer so formidable, and the rich lands of the Ukraine were open for settlement. Serfdom was an effort to keep peasants from taking advantage of this situation. (And if I've got it right, those who were venturesome enough to run away and set up outside the system became Cossacks.)
Meanwhile, the New World opened in the west. Sure enough, the colonizing powers tried various forms of indentured servitude - making serfs of the Indians in Spanish territories, bringing over indentured servants in Virginia. But eventually they hit on a better solution, from their point of view: importing slaves from Africa.
Here's the puzzle. In Europe circa 1100, with population scarce, serfdom was useful to the ruling class. By 1300 it wasn't, and had been allowed to drift away. But after 1348 it should have been worthwhile again. Yet it wasn't effectively reimposed. There were attempts to restrain wages and limit labor mobility, as well as attempts to tax the peasants (Wat Tyler's rebellion fits into all this.) But all-out feudalism didn't return. Why? And an even bigger question: why hasn't indentured servitude made a comeback in the modern era? Yes, I know, human rights and all that - but if it was profitable to have indentured servants in the modern world, I'm sure that Richard Scaife's think tanks would have no trouble finding justifications, and assorted Christian groups would explain why it's God's will.
Anyway, have to get back to real work. But try to find a copy of Domar's paper and read it.