The reason economics isn’t a real science is that you can’t conduct experiments. Chemists and biologists can bung different mixtures into test tubes or petri dishes and watch what happens. Ethics, regrettably, prevent economists from messing with people’s lives in a similar fashion.
Sometimes, however, policymakers create “natural experiments”, where the rules change on one side of a border, and economists can study how the difference affects outcomes. That happened in New Jersey on April 1 1992, when the state raised its minimum wage from $4.25 an hour to $5.05. Neighbouring Pennsylvania, where the minimum wage didn’t change, provided the control.
Two economists, David Card and Alan Krueger, realised this provided an opportunity to put to the test one of the core beliefs of conventional
