The absence of an agreed-upon standard for judging the just rate of mobility is typically dealt with by comparing America’s rate of mobility to those of other Western democracies. The highly publicized claim that social mobility in the U.S lags far behind that of other nations stems from a widely cited comparative analysis conducted 10 years ago, which placed the U.S.’s rate of mobility next to last among nine wealthy industrial democracies. However, in 2014 a team of economists from the U.S. Department of the Treasury, Harvard University, and the University of California, Berkeley examined almost 50 million tax returns in what is arguably the most extensive and rigorous study of social mobility to date.

Calculating three alternative measures of mobility, the researchers offered persuasive evidence that the United States has one of the highest rates of mobility in the world, ranking fourth, just behind Finland, Denmark, and Norway. Moreover, the findings showed no decline in the rate of social mobility among children born in the U.S. over the last 40 years. (Within the overall rate, however, the degree of mobility varied among 709 geographic districts throughout the country. The four characteristics most significantly related to these geographic discrepancies were an area’s racial segregation, high-school dropout rates, percentage of households with single mothers, and amounts of community involvement, as measured by factors such as voter turnout and participation in local organizations. Among these characteristics, the share of children in single-parent families was the strongest and most robust predictor of differences in social mobility.)

As for movement up the income ladder, the Harvard-Berkeley study revealed that children born to parents in the bottom fifth of the income distribution had a 9 percent chance of making it to the top quintile. That may sound dismal, but in judging this movement by international comparisons it’s important to bear in mind that the range of incomes varies among countries. When the income ladders differ in height, it takes a greater increase over a father’s earnings for his son to move up one income quintile on the taller ladder—and the U.S.’s income ladder is one of the tallest in the world.

So, rather than comparing how one’s income ranks relative to others all across the country, it would be wiser to focus on an absolute measure of social mobility, one that describes an individual’s changing level of prosperity over time. After all, average citizens are typically unaware of whether the rate of relative social mobility has gone up or down; they do, however, have a keen appreciation of whether their material standard of living is better than what they experienced as a child under their parents’ roof.

In this regard, America is doing quite well. According to the Brookings Institution, 67 percent of Americans born in 1968 had higher levels of real family income between 1995 and 2002 than their parents had a generation earlier. The overall proportion of children who were better off than their parents increased to 81 percent when incomes were adjusted for family size; most of those who were not better off than their parents were born to families with the highest incomes. When broken down into upper and lower income groups, four out of five children from the bottom fifth of the income distribution had higher family incomes than their parents. The median income for this group was twice as high as that of their parents. Moreover, the U.S. remains one of the only places in the world where the children of immigrants regularly go on to achieve a socioeconomic profile mirroring that of the general population—as adults, they have similar median incomes, college graduation rates, rates of homeownership, and poverty rates as the nation as a whole.