[This month, I'm serializing my 2003 Harvard Law Review article, The Mechanisms of the Slippery Slope.]
Experience with a policy can change people's empirical judgments about policies of that sort, and this can of course be good. Sometimes, though, people learn the wrong lesson, because they err in evaluating an experiment's results. For instance, suppose that after A is enacted, good things happen: stringent enforcement of a drug ban is followed by reduced drug use; an educational reform is followed by higher test scores; a new gun law is followed by lower crime rates.
