In and of itself, social mobility is far from ambiguously good. Imagine a society of 10 individuals ranked by income from the poorest, No. 1, to the richest, No. 10. Assume that a good government (the one you would prefer) jacks up the income of No. 3 to between that of No. 6 and No. 7, putting its favorite in the 6th income slot. No. 3 has now become No. 6; No. 4, No. 5, and No. 6 have all fallen down one slot. The government could increase social mobility more if, from the same starting point, it moved each odd-numbered individual one rank up and, consequently, each even-numbered individual fell one rank down: half the population would have been mobile up and half mobile down.

Relative social mobility up is necessarily accompanied by social mobility down. Few people would consciously argue that social mobility in this sense is unambiguously good, especially if the arguer is among the downward-mobile. Whether relative social mobility is good or bad must depend on its causes and consequences.

If people switch relative places but the absolute incomes of all move up in the process, social mobility can be said to be absolute: everybody gains. Economists would say that the new distribution is a Pareto-improvement if everybody gains or at worst stays put, and nobody loses. Note that the only social mobility that will eliminate envy is complete immobility when everybody earns exactly the same income. That’s the only way for everybody to be in the middle class, although in reality the equalizers would probably fare better than the equalized. The main point here, however, is that what people generally want is economic growth, not relative social mobility per se. (In a free society, ascetic choices are of course allowed too.) A widespread measure of absolute social mobility is the probability that a child will grow up to earn more than his parents.

One way to avoid clear thinking about social mobility is to loosely equate it with “equality of opportunities.” Cecilia Rouse, chairwoman of President Biden’s Council of Economic Advisors, declared to The Economist (“The Democrats’ Social-Spending Package Cannot Repair the American Dream,” November 6, 2021):

Most would agree that our current rates of social mobility are too low. There is not equality of opportunity. Kids are not starting at the same place.

That “kids” all start at the same place is of course impossible (see Anthony de Jasay, Social Justice and the Indian Rope Trick, Liberty Fund, 2014). Even if, as some 19th-century French revolutionaries wanted, the state stole children from their parents in order to educate them in a perfectly egalitarian way, young adults would not start at the same starting gate. Besides genetic factors, the state’s educators would not be all equally competent or they would themselves form a new aristocracy and fight hard to protect their privileges. If we follow James Buchanan and most classical liberals, this does not mean that some minimal education should not be available to all children.

Social mobility, then, is not a fundamental or ultimate value. It is an instrumental or secondary value. It is valued as a consequence of individual liberty and an accessory of general prosperity. Individuals thriving to improve their conditions generate social mobility and constant disruptions of old ways of doing things, and disruptions are necessary for economic growth. In competing to offer consumers (individuals in their consumer activities) what they want at the lowest possible prices, producers (individuals as producers) continuously jostle the distribution of income. In the process, the absolute incomes of nearly everybody increase or are anyway maintained much higher than they would be in an unfree society.

A related argument is given by Friedrich Hayek, who shows that, in a free society, nobody can have a guaranteed position in the distribution of income (or in the social ranking, which I have assumed to be coextensive with the distribution of income, which is not always true). The shuffling of relative positions, that is, relative social mobility is necessary for economic prosperity. A short quote from his Law, Legislation and Liberty, Vol. 2: The Mirage of Social Justice (University of Chicago Press, 1976, p. 94) may serve as an introduction:

The frequent recurrence of such undeserved strokes of misfortune affecting some group is, however, an inseparable part of the steering mechanism of the market: it is the manner in which the cybernetic principle of negative feedback operates to maintain the order of the market. It is only through such changes which indicate that some activities ought to be reduced, that the efforts of all can be continuously adjusted to a greater variety of facts that can be known to any person or agency, and that the utilization of dispersed knowledge is achieved on which the well-being of the Great Society rests. …

If we were all to be consistently deprived, as the socialists proposed to do, of all ‘unearned benefits’ which the market confers upon us, we would have to be deprived of most of the benefits of civilization.