I'm gonna add - understanding feedback loops. A lot is written about economics and politics by people who don't seem to get that one, and those discussions are mostly pointless. Myself I understood it only after control theory course in university, though now I recognize that high-school level chemistry teaches it too (chemical equilibrium). After you grok it you start to see how incentives can feed one another and that it's perfectly reasonable for a bad system to exist in which there is no single actor to assign blame to (compare: is television stupid because people are dumb, or are people dumb because TV is stupid?).