James Anthony Downs (November 21, 1930 – October 2, 2021) was an American economist specializing in public policy and public administration. His research focuses included political choice theory, rent control, affordable housing, and transportation economics. He wrote a number of books including, An Economic Theory of Democracy (1957) and Inside Bureaucracy (1967), which have been major influences on the public choice school of political economy. In Downs's Law of Peak-Hour Traffic Congestion (1962), he predicted that expanding expressways could not reduce traffic congestion, since demand would increase as well, and that reducing speeds increases capacity.

He served as a senior fellow at the Brookings Institution in Washington, D.C., member of faculty at the University of Chicago and a visiting fellow at the Public Policy Institute of California in San Francisco. Downs was also an elected fellow of the National Academy of Public Administration.

James Anthony Downs was born on November 21, 1930, in Evanston, Illinois. His father was the founder of a consulting firm, Real Estate Research Corporation, and a frequent speaker on real estate related topics. He grew up in Park Ridge, Illinois, a suburb of Chicago.

He received a B.A. in international relations and political theory from Carleton College in 1952. During this time he was the elected president of the college student body. He would later credit this experience for some of his interests in studying democracy. He went to the Graduate School of Business at Stanford University on a scholarship to pursue his M.A. and Ph.D. in economics, obtaining his doctorate in 1956.

He enlisted in the Navy and served as an intelligence officer when he was drafted. During this time he also served on an aircraft carrier in the Mediterranean Sea. He quit the service after three years to join his father's consulting firm and also briefly served as a member of the faculty at the University of Chicago.

Downs served as a consultant to many of the nation's largest corporations and public institutions, including the U.S. Department of Housing and Urban Development (HUD) and the White House. President Lyndon B. Johnson appointed him to the National Commission on Urban Problems in 1967, and HUD Secretary Jack Kemp appointed him to the Advisory Commission on Regulatory Barriers to Affordable Housing in 1989. He was an officer or trustee of the NAACP Legal Defense and Educational Fund.

In his seminal work, An Economic Theory of Democracy (1957), Downs introduced a left–right axis to economic theory. On the "left" he placed communist parties that want entirely state-planned economies, and on the "right" he placed conservative parties that demand an entirely deregulated economy.

He claimed that most voters have incomplete information when voting for political candidates in a democracy, and therefore will resort to economic issues of "how much government intervention in the economy there should be" and how parties will control this. Downs borrowed the curve from Harold Hotelling, who developed it to explain how grocery stores targeted customers. Downs's book has since become one of the most cited books in political science. His left–right axis model has been integrated into the median voter theory first articulated by Duncan Black.