Quick: If you take out a $1000 loan that has a 20% rate, how much will you owe a year in interest?

Answer: $200. But if you got that wrong, you’re not alone. Nearly two thirds of Americans can’t calculate interest payments correctly, according to a new study. About a third said they didn’t even know how.

One of the silver linings of the financial crisis was that it was supposed to have taught many Americans a lesson, albeit painful, about the dangers of debt, and financial issues in general. Apparently, the message, though, didn’t get across.

All told, a new study, which was released today, estimated that nearly two-thirds of Americans couldn’t pass a basic financial literacy test, meaning they got fewer than four answers correct on a five-question quiz. Worse, the percentage of those who can pass the test has fallen consistently since the financial crisis to 37% last year, from 42% in 2009.