Sumner received a PhD in economics from the University of Chicago in 1985. His published research focuses on prediction markets and monetary policy. In the wake of the 2008 financial crisis, Sumner began authoring a blog where he vocally criticized the view that the United States economy was stuck in a liquidity trap. Sumner advocates that central banks such as the Federal Reserve create a futures market for the level of nominal gross domestic product, and adjust monetary policy to achieve a nominal income target on the basis of information from the market. Monetary authorities generally choose to target other metrics, such as inflation, unemployment, the money supply or hybrids of these and rely on information from the financial markets, indices of unemployment or inflation, etc. to make monetary policy. In 2015, Sumner published The Midas Paradox: A New Look at the Great Depression and Economic Instability. The book argued that the Depression was greatly extended by repeated gold market shocks and New Deal wage policies.
Sumner contends that inflation is "measured inaccurately and does not discriminate between demand versus supply shocks" and that "Inflation often changes with a lag...but nominal GDP growth falls very, very quickly, so it'll give you a more timely signal stimulus is needed". He argued that monetary policy can offset fiscal austerity policies such as those pursued by the British government in the wake of the 2007 economic crisis. In April 2011, the Reserve Bank of New Zealand responded to Sumner's critique of inflation targeting, arguing that a nominal GDP target would be too technically complicated, and make monetary policy difficult to communicate. By November 2011, however, economists from Goldman Sachs were advocating that the Federal Reserve adopt a nominal income target. Nathan Sheets, a former top official at the Federal Reserve and the head of international economics at Citigroup, proposed that the Federal Reserve adopt a nominal consumption target instead. Sumner has argued that one cannot account for the impact of fiscal policy without first considering how monetary policy may affect the outcome; fiscal stimulus may not succeed if monetary policy is tightened in response. Economic journalists have referred to this as the Sumner Critique, akin to the Lucas critique. Summarizing this thinking, The Economist suggested that
Personal life
Well known in Bentley's economics department as a "technophobe," Sumner, who purchased his first cell phone in 2011, apparently "triggered expressions of surprise and amusement when he informed his colleagues that he was starting a blog."