Notes from a presentation by Clark last year containing "work in progress from a planned book on social mobility over the long run" (pdf):
What is the fundamental nature of human society? Is it stratified into enduring layers of privilege and want, with some mobility between the layers, but permanent social classes? Or is there, over generations, complete mobility between all ranks in the social hierarchy, and complete long run equal opportunity? [. . .]
This book systematically exploits a new method of tracing social mobility over many generations, surnames, to measure the persistence of classes over as much as 800 years, 24 generations. It looks at societies where surnames are inherited, unchanged, by children from fathers. In such cases they thus serve as a tracer of the distant social origins of the modern population (and interestingly also as a tracer of the Y chromosome).
In this role surnames are a surprisingly powerful instrument for measuring long run social mobility. The results they reveal are clear, powerful, and a shock to our casual intuitions.
(1) In England, where we can trace social mobility back to 1066 using surnames, there were never any long persistent ruling and lower classes for the indigenous population: not in medieval England, and not now. About 5-6 generations were, and are, enough to erase most echoes of initial advantage or want. For the English class is, and always was, an illusion. Histories such as those of the Stanley family turn out to be rare exceptions, not the rule.
(2) Paradoxically, while England reveals complete long run mobility, the rates of social mobility per generation, better measured by looking over multiple generations, turn out to be lower than is conventionally estimated. But the mathematics of mobility is such that even such slow regression to the mean, over time, will completely erase initial advantage and want.
(3) The rate of social mobility in England was as high in the middle ages as it is now. The arrival of the whole apparatus of free public education in the late nineteenth century, and the elimination of nepotism in government and private firms, has not improved the rate of social mobility.
(4) The extraordinarily complete long run mobility of England is likely typical of other western European societies. But other countries, in contrast, do exhibit persistent social classes over hundreds of years. In the US, for example, the Black population has persisted at the bottom of the social order, and the Jewish population at the top. In Chile surname evidence shows the indigenous population has remained at the bottom since the Spanish conquest of 1541. [. . .]
(7) Though parents at the top of the economic ladder in any generation in preindustrial England did not derive any lasting advantage for their progeny, there was one odd effect. Surname frequencies show was that there was a permanent increase in the share of the DNA in England from rich parents before 1850. After 1850 a frequency effect operated, but in reverse. Surname frequencies show the DNA share of families in England who were rich in 1850 declined relative to that of poor families of the same generation by 2010. [. . .]
What is the meaning and explanation of these results? This is a much more contentious and difficult area. The book argues for the following conclusions:
A. Why can’t the ruling class in a place like England defend itself against downwards mobility? If the main determinants of economic and social success were wealth, education and connections then there would be no explanation of the consistent tendency of the rich to regress to the society mean. Only if genetics is the main element in determining economic success, if nature trumps nurture, is there a built-in mechanism that ensures the observed regression. That mechanism is the intermarriage of the rich with those from the lower classes. Even though there is strong assortative mating, since this is based on the phenotype created in part by chance and luck, those of higher than average innate talent tend to systematically mate with those of lesser ability and regress to the mean.
B. Racial, ethnic and religious differences allow long persisting social stratification through the barriers they create to this intermarriage. Thus for a society to achieve complete social mobility it must achieve cultural homogeneity. Multiculturalism is the enemy of long run equality.
We can even push back the study of mobility in medieval England to 1066 using surnames. In particular the Domesday book of 1086, and associated charters and other documents, allows us to identify a subset of English names which are of Norman origin only, and which were held by the new ruling class installed by William I (Keats-Rohan, 1999). These names include such well known English names as Balliol, Baskerville, Darcy, Glanville, Lacy, Mandeville, Percy, Sinclair, and Venables. Most of these names were drawn from the home village of a member of William’s invasion force in Normandy, Brittany or Flanders. Thus Baskerville is from the village of Bacqueville in Normandy, Venables from Venables, Ivry from Ivry-la-Bataille. As the ruling class imposed by force in 1066, how quickly was this group assimilated into the general population in medieval England?
A group of 236 names of this form was compiled. The frequency of these names in the later medieval population (1368-1449) was estimated at 0.9 percent based on a sample of enrollment lists for English armies and garrisons. What was the relative representation of this conquering elite at Oxford university by the thirteenth century, assuming their name share in the general population was 0.9 percent? Figure 3.4 shows this by 20 year periods from 1180. In the thirteenth century these surnames were on average three times as frequent at the university as in the general population. However, their representation fell rapidly in the fourteenth century, so that by the late fourteenth century these names were only about 10 percent more common at the university than in the general population. This would seemingly imply that the Domesday elite of 1086 had by 1350, less than 300 years later, descended in status on average to the level of the general population. But we shall see that there is contradictory evidence in this case. Among the fighting elite of 1368-1449 the names of these original Norman warriors continue to be greatly overrepresented.