THE “Great Gatsby curve” is the name Alan Krueger, an economic adviser to Barack Obama, gave to the relationship between income inequality and social mobility across the generations. Mr Krueger used the phrase in a 2012 speech to describe the work of Miles Corak of the University of Ottawa, who has shown that more unequal economies tend to have less fluid societies. Mr Corak reckons that in some places, like America and Britain, around 50% of income differences in one generation are attributable to differences in the previous generation (in more egalitarian Scandinavia, the number is less than 30%).
Even that may paint too rosy a picture. Mr Corak’s work draws on recent studies that compare income levels between just two generations: fathers and sons. That is out of necessity; good data covering three or more generations are scarce. But reliance on limited data could lead to overestimates of social mobility.
Gregory Clark, an economist at the University of California, Davis, notes that across a single generation some children of rich parents are bound to suffer random episodes of bad luck. Others will choose low-pay jobs for idiosyncratic reasons, like a wish to do charitable work. Such statistical noise makes society look more changeable than it is. Extrapolating the resulting mobility rates across many generations gives a misleadingly sunny view of long-term equality of opportunity. Mr Clark suggests that family history has large effects that persist for much greater spans of time. Fathers matter, but so do grandfathers and great-grandfathers. Indeed, it may take as long as 300-500 years for high- and low-status families to produce descendants with equal chances of being in various parts of the income spectrum.
Mr Clark confronts the lack of good data by gleaning information from rare surnames. You can tease mobility trends from surnames in two ways. One method relies on past links between certain names and high economic status. In a 2012 paper, for instance, Mr Clark examines prosperous Swedes. The unusual surnames of 17th-century aristocrats and the Latinised surnames (such as Linnaeus) adopted by highly educated 18th-century Swedes are both rare in the Swedish population as a whole. By tracking the overrepresentation of those names in elite positions, he is able to work out long-run mobility rates.
As late as 2011 aristocratic surnames appear among the ranks of lawyers, considered for this purpose a high-status position, at a frequency almost six times that of their occurrence in the population as a whole. Mr Clark reckons that even in famously mobile Sweden, some 70-80% of a family’s social status is transmitted from generation to generation across a span of centuries. Other economists use similar techniques to reveal comparable immobility in societies from 19th-century Spain to post-Qing-dynasty China. Inherited advantage is detectable for a very long time.
A second method relies on the chance overrepresentation of rare surnames in high- or low-status groups at some point in the past. If very few Britons are called Micklethwait, for example, and people with that name were disproportionately wealthy in 1800, then you can gauge long-run mobility by studying how long it takes the Micklethwait name to lose its wealth-predicting power. In a paper written by Mr Clark and Neil Cummins of Queens College, City University of New York, the authors use data from probate records of 19th-century estates to classify rare surnames into different wealth categories. They then use similar data to see how common each surname is in these categories in subsequent years. Again, some 70-80% of economic advantage seems to be transmitted from generation to generation.
Mr Clark’s conclusion is that the underlying rate of social mobility is both low and surprisingly constant across countries and eras: the introduction of universal secondary education scarcely affects intergenerational mobility rates in Britain, for example. This consistency, he suggests, shows that low mobility may be down to differences in underlying “social competence”. Such competence is potentially heritable and is reinforced by the human tendency to mate with partners of similar traits and ability.
Bob’s your uncle, unfortunately
This is a distressingly fatalistic view of opportunity. Studies using the few multi-generation datasets that exist offer a slightly more encouraging picture. A Swedish analysis of the city of Malmo, using data covering individual families over four generations, finds a meaningful relationship between a child’s educational attainment and that of his great-grandparents, more evidence that a look at just one generation leads to overestimates of mobility. By subjecting the same data to a surname analysis, Mr Clark calculates that 60% of income differences in Malmo are attributable to economic advantages in previous ones—lower than his own rate but still higher than Mr Corak’s single-generation estimates.
Painstaking work by Jason Long of Wheaton College and Joseph Ferrie of Northwestern University provides another perspective. They have spent the past decade poring over census returns from America and Britain, identifying families with children in one count, tracking down the same children as adults in another, and thereby building up a multigenerational dataset. An analysis of three generations shows that in both America and Britain the effect of high (or low) incomes in one generation lasts for at least two more. Yet their study also suggests it is possible to break patterns of immobility. Although American and British mobility rates had converged by the middle of the 20th century, America’s social order was considerably more fluid than Britain’s in the 19th century. The past has a tight grip on the present. But in the right circumstances, it can apparently be loosened.