Too many economists excuse their practical failure by saying "the politicians (or bureaucrats) didn't do exactly what I recommended." Just as medical practitioners must allow for the fact that their patients may not take all the pills they prescribe, or follow all the advice they are given, so economics practitioners need to foresee political and administrative pressures and make their plans robust to changes that politicians, bureaucrats, and lobbyists are likely to impose.
Paul Klemperer
economics, market-design