Much as doctors understand diseases but cannot predict when you will fall ill, economists’ fundamental mission is not to forecast recessions but to explain how the world works. Over the next six weeks we will be running a series of briefs on important economic theories that did just that—from the Nash equilibrium, a cornerstone of game theory, to the Mundell-Fleming trilemma, which lays bare the trade-offs countries face in their management of capital flows, exchange rates and monetary policy; from the financial-instability hypothesis of Hyman Minsky to the insights of Samuelson and Wolfgang Stolper on trade and wages; from John Maynard Keynes’s thinking on the fiscal multiplier to George Akerlof’s work on information asymmetry, the topic of this week’s article (see article). These breakthroughs are adverts not just for the value of economics, but also for three other things: theory, maths and outsiders.

1. Akerlof’s market for lemons Secrets and agents

2. Minsky's financial cycle Minsky’s moment

3. The Stolper-Samuelson theorem An inconvenient iota of truth

4. The Keynesian multiplier Where does the buck stop?

5. The Nash equilibrium Prison breakthrough

6. The Mundell-Fleming trilemma Two out of three ain’t bad