Thanks to a research team led by Harvard and Stanford professors, the traditionally abstract concept of the American Dream is now measurable. There is data to show just how few Americans are earning more money than their parents did.

The numbers don't look good for young people.

Those born in 1980, or today's 30-year-olds, have just a 50% chance of making more money than their parents.

By contrast, a kid born in 1940 had a 92% chance of earning more than their parents at the same age. For kids born in 1950, the likelihood of achieving that version of the American Dream had fallen to 79%. By 1960, that figure had dropped further to 62%.

Check out the chart provided by The Equality of Opportunity Project: