A child born to parents in the bottom income quintile in the United States has approximately a 7–8 percent chance of reaching the top quintile as an adult. In Denmark, the same chance is roughly 12 percent. In Canada, about 13 percent. These numbers — from Raj Chetty's landmark Equality of Opportunity research — quantify what social mobility means in practice: how often does a society's economic ladder allow people to climb to rungs their parents didn't reach? The answer matters not just for individuals but for the broader case that a market economy is fair: high inequality is more acceptable if mobility is high; low inequality is less necessary if mobility is robust. In the United States, both inequality and immobility have increased together — a combination that challenges any narrative of America as uniquely open to individual advancement.
In plain terms
Social mobility is the ability of individuals to move up or down the economic hierarchy relative to the position they were born into. It has two main dimensions:
Intergenerational mobility: how much a child's economic outcome differs from their parents'. Measured by the intergenerational income elasticity (IGE) — the correlation between parents' and children's log income. A high IGE (close to 1) means children tend to end up near their parents' income level; a low IGE (close to 0) means parental income has little predictive power over the child's outcome.
Relative mobility: the probability of moving from one quintile or decile to another across generations — specifically, of escaping the bottom quintile or reaching the top.
Absolute mobility: whether children are better off in absolute terms than their parents at the same age — real income higher than parents had at equivalent life stages.
Raj Chetty and colleagues at Opportunity Insights have produced the most comprehensive U.S. mobility research, using IRS tax records linked across generations. Their Opportunity Atlas data documents mobility rates at the county and census tract level — revealing that where you grow up in America matters enormously for your long-run outcomes.
Why it works this way
Low mobility reflects the persistence of economic advantage and disadvantage across generations through several channels:
Educational access: children from higher-income families attend better-resourced schools, have access to tutoring, and are more likely to complete college. The College Board's higher education access data documents persistent gaps in college enrollment and completion by income quartile.
Geographic concentration: Chetty's research shows that mobility varies by a factor of five across U.S. commuting zones — children raised in the Southeast and industrial Midwest have far lower mobility than those raised in the Great Plains and Pacific Northwest. This geographic variation is driven by school quality, social capital, family structure, and local economic opportunity.
Intergenerational wealth transfers: capital ownership is highly concentrated; inheritances and inter vivos transfers give children of wealthy families starting advantages (down payments, startup capital, network access) that cannot be replicated through labor income alone.
A real example
Chetty's finding that absolute mobility — the fraction of children who earn more than their parents at the same age — has fallen from over 90 percent for children born in 1940 to about 50 percent for children born in 1984 is among the most discussed findings in recent economics. The Opportunity Insights research attributes the decline primarily to rising income inequality rather than lower growth rates — even if average incomes kept growing, the growth was so concentrated at the top that fewer people shared in the upward trend.
Why it matters
Social mobility is the test of whether inequality is compatible with broadly shared opportunity. High inequality combined with high mobility can be consistent with fairness; high inequality combined with low mobility reflects an economy where birth circumstances heavily determine life outcomes. The measurement and understanding of mobility determines whether policies targeting inequality, education, housing, and early childhood investment are well-targeted — and whether the opportunity premise of a market economy is credibly fulfilled.
