I am currently seeking to develop common criteria to evaluate the success of different policy initiatives to tackle the informal economy. To do this, one needs to develop a common measuring rod (e.g., the cost per job moved from the informal economy into the formal economy; the tax revenue-to-cost ratio). The first thing that struck me is whether it is valid to use such criteria to evaluate a policy when it was not perhaps its original objective. The second thing is to select common criteria that can be used. What common measure/s would you use? And does anybody know any literature that discusses the issues involved in developing common measures to compare different policy initiatives?