Gregory Clark is a professor of economics at the University of California, Davis. His research centers around economic history, with his work on the Industrial Revolution in Britain culminating in his book, "A Farewell to Alms."

His new book, "The Son Also Rises" (Clark is a big fan of Hemingway puns), traces families with particular surnames to measure social mobility over the course of hundreds of years in England, the United States, Sweden, India, China and more. He finds that there's much less mobility than we often assume, and that government interventions to promote it more often than not fail. We spoke on the phone Monday afternoon; a lightly revised transcript follows.

What gave you the idea to look at surname data?

Initially I was interested just in extending conventional social mobility estimates into the distant past. Estimating social mobility is very data intensive. You need to link individual parents and children. There are thus no such estimates for any society before 1850.

Tracking surname status was a convenient shortcut. In most societies, all the people with a surname such as Goodhart descended from the earlier set of Goodharts. We do not know the individual linkages, but we can ask what is happening to their status as a group across generations.

And what did you find in collecting this surname data?

I found that you get radically slower estimated mobility rates for all societies when you switch to surnames. The conventional estimates of status correlation across generations are 0.2-0.6 [so your parentage explains 4-36 percent of your social status, income, etc. --  Dylan]. With surname groupings it is always 0.7-0.8.

The effect is dramatic in some countries. Modern Sweden has some of the most rapid social mobility rates estimated in the world. Yet surnames in modern Sweden show status persistence exactly in this 0.7-0.8 range. This result was completely unexpected. Understanding why that is the case is a key puzzle the book tackles.

You don't just look at income either. You look at educational attainment, what occupation they're in, etc.

The book mainly concentrates on measures such as education, occupational status, wealth and longevity as indicators of status. Another surprising puzzle that emerged is that with surnames, the persistence of status was the same for all these measures.

We might expect wealth to persist in a different way, since it can be transmitted across generations in a different way than education. You do not need any talent to inherit wealth. This is another regularity the book tries to account for.

How accurate is the surname data, relative to more conventional estimates?

I have a polyglot collection of data, and the accuracy varies. In cases such as England, where we have the records of most people who attended Oxford and Cambridge 1200-2013, the accuracy can be within 0.01 in terms of the measured correlation.

In other cases – China, for example, where there are very few surnames -- the accuracy is only within 0.1. But everywhere you can reject the idea that social mobility rates are as fast as conventional estimates.

To be clear, we're speaking in relative terms here, right? So we're trying to find out what determines people's relative standing given that they are a part of a particular society?

Mostly we measure status in terms of where are you in the overall distribution of status, measured by such things as whether you attend an elite university or have a high-status occupation such as doctor or attorney.

You generally found that governmental intervention didn't do much. Were there any exceptions to that trend?

Another remarkable feature of the surname data is how seemingly impervious social mobility rates are to government interventions. In all societies, what seems to matter is just who your parents are. At the extreme, we see in modern Sweden an extensive system of public education and social support. Yet underlying mobility rates are no higher in modern Sweden than in pre-industrial Sweden or medieval England.

There was one case where government interventions did seem to promote mobility, which was in Bengal, in India. There the strict quota system in educational institutions had benefited significantly people with surnames associated with the Scheduled Castes.

But the bizarre element here is that these quotas did not help those truly at the bottom of the social ladder. Instead, the benefits went to families of average social status whom the British had mistakenly classified as Scheduled Caste. These families have now become a new elite. The truly disadvantaged, such as the large Muslim community, have been correspondingly further burdened by being excluded from these quotas.

Interestingly, in China, the extreme social intervention represented by the Communist Revolution of 1949, which included executing large numbers of members of the old upper class, has not resulted in much of an increase in social mobility. Surnames of high status in the Imperial and Republican era continue to be overrepresented among modern elites, including Communist Party officials.

The families that have high social competence, whatever the social system is, typically find their way to the top of the social ladder.

So what's driving this? Why is social status so sticky?

This is intellectually the most intriguing part of the story, and it's one that's hard to make a lot of progress on.  It is clear that families are very powerful determinants of children’s outcomes. But what do parents transmit to their children? Is it mainly some type of culture? Or is it mainly genetics?

The data does not exist to provide any conclusive answer to this question. But even if this is cultural transmission, it looks in all respects just the same as biological inheritance. The book performs a series of tests to see if biological transmission can be ruled out as the important link, and the empirical patterns never rule this out.

For example, if biological transmission is the most important, then elite groups will never be the product of the adoption of particular cultural traits. Instead they will always represent a selection from the upper end of abilities of a parent population. Modern Jews will not be elite because of the social and religious mores of Judaism, but because they are a selection based on ability from a larger parent Jewish population.

For all such elite groups we observe, they do indeed turn out to be a selection from a larger population. Egyptian Copts are such a social elite, for example, but they represent the descendants of the Copts rich enough at the time of the Arabian conquest to be able to afford the head tax levied on all who did not convert to Islam.

A recent book, "The Triple Package"  [by Amy Chua and Jed Rubenfeld], argues the extreme opposite of biology in explaining social status, with the claim that successful cultural groups in the U.S. have three key features leading to success, one being impulse control.

But what is remarkable is how disparate the culturally successful groups they identify are – Jews, Chinese, Indians, Mormons, Iranians, Lebanese, Nigerians, Cubans. And it is demonstrable that most of the successful groups identified here were elites selected from the parent populations as a combined result of politics at home and immigration policy in the U.S.

How much does this explain differences in development between societies, as opposed to within them?

All this information on social mobility within societies unfortunately does not offer much insight into why societies as a whole succeed or fail in economic terms.

There's currently something of a debate among policy writers about the extent to which mobility should be promoted through welfare state expansion (universal pre-K, greater college access, increased transfers to low-income people) versus through encouraging people to form stable family units in which to raise children. I imagine you think that's all somewhat orthogonal to the real point.

The surname data suggests that you will not be able to do much to increase social mobility through social policies of any type.  We already live in societies of massive social intervention in terms of the provision of education and health care. Yet we have not been able to raise social mobility rates above those of the pre-industrial era. Even the most interventionist societies such as Sweden have such low social mobility rates.

But if we're learning that we can predict the majority of people's outcomes at conception, that should lead us to reexamine our assumption that whatever income distribution comes out in society is fine. Because if it's the case that a lot of this is determined before someone enters the game, it weakens the case for letting the market determine the distribution. You'd be much more likely to favor a society with much less inequality.

And that's where Sweden's system does provide advantages over the U.S.'s. They haven't changed mobility rates, but they've changed the consequences, strongly, of ending up at various points in the distribution. It's a much better place for people who end up at the bottom of the distribution.

Despite social mobility being very low, you do find that elites see their position decay over time. What's driving that?

One piece of news that most people will find encouraging in these various studies is that eventually all elites become average in their characteristics, even if that takes 300 years (though there are exceptions where elites only marry endogamously [the practice of marrying within a specific ethnic group, class or social group], as in India).

Accounts that emphasize cultural transmission all have a hard time explaining why successful groups, and successful families in general, all experience regression to the mean. There is nothing to stop a cultural trait being inherited unchanged. We see the preservation of such cultural forms as religious rituals unchanged over many generations.

Only biological inheritance has an inbuilt mechanism to explain observed regression to the mean. It also has predictions about when this regression to the mean will not be observed (complete endogamy). It further implies that the rate of regression to the mean will be the same at the top of the status distribution as at the bottom.

So the biological pathway has two advantages over the cultural. It produces a mechanism to explain the regression of all elites and underclasses that we observe, and it has testable implications about the speed and character of that mobility.

Anything else you wanted to mention before we wrap up?

The final surprise in conducting this study was to find a seeming simple physics that underlies social mobility. I have been doing economics for a long time, and when we come to explaining features such as the growth rates of different societies, economics is very disappointing. We can predict little of interest.

Yet with social mobility you can observe across a variety of societies and epochs not just lawful behavior, but also laws that are simple and elegant. When we observe an elite group in 1800 in England, we can predict to seven generations in the future what their relative social position will be, despite the arrival of the Industrial Revolution and the rise of the modern welfare state in the interval.

Two very simple equations are sufficient to describe a major feature of the social world, and a feature that you would think impossible to model in any such manner.