The … issue is the competence with which the state discharges its economic functions. Does regulation of railway rates keep them at proper levels? Does review of new stock issues protect the investor from loss? Does review of the truthfulness of advertisements protect consumers? Does the federal mediation service reduce the frequency or duration of strikes? Will the review of new drugs save human lives?
George Stigler (1975). The Citizen and the State. Essays on Regulation, p. 10
I ask you to believe a strange thing. No one knows the answer to questions of this sort. At most only a tiny set of policies have been studied with even moderate care. The conservative has not found it necessary to document his charges of failure, nor the liberal to document his claims of success.