The annual cost of attending a four-year private institution in the United States reached $51,690 last year, more than double what it was less than two decades ago.

For many Americans, a college degree is often regarded as a measure of success, yet a postsecondary education has become cost-prohibitive for many young people, even when they receive financial aid. 

In order to be able to get a degree, millions of students rack up tens of thousands of dollars in debt, sometimes amassing a debt burden that will take decades to fully pay off. (Here are 50 U.S. counties with the most student debt.)

Based on data from the College Board, a nonprofit group associated with American postsecondary institutions, 24/7 Wall St. reviewed the average cost nationwide of attending both four-year public and a four-private colleges each year since 1971. Both figures include tuition, fees, and room and board.

In 1971, a four-year education at a private college in the United States cost less than one-tenth what it does today. Even after adjusting for inflation, a year of private college today costs more than two and a half times what it did back then. This means college prices are disproportionately high for potential undergraduates at a wide array of institutions, and not just at the most expensive colleges in every state.

Click here to see the cost of college the year you were born
Click here to see our detailed methodology