When I taught public policy, one of the key ideas I tried to put across was that when you create a public policy, you create a system, and vice versa. One of the reasons, I argued, that policies often produced surprising effects was that the links between different parts of these systems were not well understood. Governments necessarily operate bureaucratically, which means that the types of systems they run are disguised by the myriad classes and classifications they use to process reality. Usually, the insiders know what is going on, although for those in government trying to keep control of…