In his Carpe Diem blog post about the Jones Act, which requires the use of American ships on all domestic voyages, Mark J. Perry cites a Mercatus Center study by Thomas Grennes, Poole College professor emeritus of economics. Perry is a scholar at AEI and a professor of economics and finance at the University of Michigan’s Flint campus. Perry also cites Grennes’ study in this opinion piece in the Washington Examiner.