Scott Sumner is an American economist known for his work in monetary policy and macroeconomics. He is a professor at George Mason University and has contributed significantly to the development of the Market Monetarism school of thought, which emphasizes the importance of nominal GDP targeting. Sumner gained prominence through his blog, "The Money Illusion," where he discusses economic theories and current events. He advocates for using market expectations to guide monetary policy, arguing that central banks should focus on stabilizing the economy by targeting future nominal GDP rather than traditional inflation measures.