For the last twenty or so years,
policymakers have been enjoined to base their recommendations on evidence.
That is now uncontroversial to the point of triviality—of course
policy should be based on the facts.
But are the methods that policy makers are supposed to rely on
to gather and analyze evidence the right ones?
In Evidence-Based Policy, Nancy Cartwright and Jeremy Hardie
explain that the dominant methods now in use—methods
that imitate standard practices in medicine,
like randomized control trials—do not work.
They fail, Cartwright and Hardie contend,
because they do not enhance our ability to predict
whether policies will be effective.
Current guides for the use of evidence tend to rank
scientific methods according to the degree of trustworthiness
of the evidence they produce.
That is valuable in certain respects,
but it provides little advice about how to think about
putting such evidence to use.
Evidence-Based Policy focuses on showing policymakers
how to use evidence effectively.
It also explains what types of information are most necessary for making
reliable policy and offers lessons on how to organize that information.
