A dead economist’s ideas are alive and well in ag policy debate.   Many policy ideas, especially related to taxation, are attributed to “dead economists.” One of the pioneers in tax theory fitting this mold is Arthur Pigou, an unlikely influencer on agricultural and food policy. That point was driven home yesterday by a speech at Iowa State University given by African Development Bank President Akinwumi Adesina, the former agriculture minister of Nigeria who will be presented with the 2017 World Food Prize this week at the Iowa Hunger Summit. First, however, who was Pigou? He was a British economist who followed up on his Cambridge professor’s work in defining “externalities,” or what introductory...