A Nobel for experimental economics

Card's most famous paper, comparing unemployment in New Jersey and Pennsylvania, showed that economic theory was wrong about the minimum wage — that raising it could have little or no effect on unemployment, in the real world.

• Other natural experiments found by the winners involved things like the lottery number individuals received in the Vietnam War draft, or — in the case of a paper that Alex Tabarrok calls "one of the most beautiful in all of economics" — the month that people were born in, which has a small but significant effect on how much education they receive.

The bottom line: If economics has any claim to being a science, it has to be falsifiable. Card, in falsifying at least one economic theory, arguably helped make his subject a science.