It's possible to divide policy positions into two broad categories:
X is good/bad - for example:
- Smoking is bad
- Home-ownership is good
- Bovine tuberculosis is bad
X will encourage/discourage Y - for example:
- Higher taxes on cigarettes will discourage smoking
- Low interest rates will encourage home-ownership
- Systematic culling of badgers will reduce bovine tuberculosis
I'm interested here in the second of these. Policies along the lines of "X will encourage Y" can in many cases be empirically tested; for example, by randomly selecting geographical areas in which to implement badger culls, and rigorously studying their effectiveness.
The impression I get is that politicians are resistant to such methodical studies, and implement them only as a response to opposition to policies they wish to implement, subsequently ignoring the results if they aren't "right".
Are there any states, regions, etc. where those in power are or have been bound (either by statute or manifesto commitment) to subject policy to empirical study? And if so, are there instances where a policy found to be ineffective has been abandoned?