There’s not agreement on what’s desirable, but there’s agreement of what the goals of a piece of legislation are. Often, those goals area measurable. The scale of experimentation that would be required to scientifically test whether legislation does what it’s supposed to do would be massive, but I’d bet it would be worthwhile.
Sure, but the problem is there are unintended consequences that you don't even think of until after passing the law. Sure you can measure metrics, but only the metrics you know to measure, not ones that you didn't think of.
