A university degree increases an American's lifetime earnings by nearly $1 million (£630,000), a US Census Bureau report says.
University graduates earn almost twice as much as non-graduates. People with professional degrees earn $2.1 million on top of that. And the gap in earnings is growing.
"At most ages, more education equates with higher earnings, and the payoff is most notable at the highest educational levels," said Jennifer Cheeseman Day, co-author of the report.
Universities quickly seized on the findings to defend their spiralling tuition fees. An undergraduate degree at a private four-year university costs about $140,000.
Institutions also said more young people should be encouraged to go to college. But critics said it did not make sense to produce more university graduates when fewer than a third of all jobs require a university education.
The estimates of lifetime earnings, which were released last week, are based on 1999 income projected over a typical work life, which is considered to span the ages 25 to 64. About a quarter of Americans aged 25 and over have a degree. Graduates with bachelors degrees can expect to earn $2.1 million during their careers, those with masters degrees $2.5 million, and those with degrees in medicine, law and other professional areas $4.4 million.
Working Americans without a degree are projected to have lifetime earnings of $1.2 million.
The census, which the US conducts every ten years, also found disparities between men and women who attended university. Men with professional degrees can expect to earn almost $2 million more than women with the same level of education. Ms Day said this was in part because more men held executive positions and more women than men quit work to care for children.
That gap is narrowing, however, and the census found that more women than men have been receiving university educations every year since 1982.
Black and Hispanic Americans continue to earn less than whites with comparable educations.
Among Americans with bachelors degrees, those who work in engineering earn the most. Those in education make the least.