The central insight of public choice economics comes from the observation that when some issue in society is turned over to the government for the government to supervise, the government employees do not manage the issue for the maximum benefit of society as a whole. The concept is explained in the article Public Choice Economics in the Concise Encyclopedia of Economics:
"Although most people base some of their actions on their concern for others, the dominant motive in people’s actions in the marketplace—whether they are employers, employees or consumers—is a concern for themselves. Public choice economists make the same assumption—that although people acting in the political marketplace have some concern for others, their main motive, whether they are voters, politicians, lobbyists or bureaucrats is self-interest. In James Buchanan’s words the theory "replaces romantic and illusory notions about the workings of governments with notions that embody more skepticism."
A Christian summary of the theory would be that even government employees are marked by original sin.