Short answers, pulled from the story.
Alvin Harvey Hansen was an American economist who taught at Harvard University and is often called "the American Keynes" because he introduced and popularized Keynesian economics in the United States during the 1930s and 1940s, more effectively than any other economist. He translated, extended, and domesticated the ideas in Keynes's The General Theory for American audiences, policymakers, and students.
Hansen's best-known theoretical contribution was co-developing the IS-LM model with John Hicks, a diagram used in economics to show how fiscal and monetary policy affect national income. He also formulated the secular stagnation thesis, arguing that mature economies tend toward long-term stagnation without sustained government demand-side intervention. His 1941 book Fiscal Policy and Business Cycles was the first major American work to fully support Keynes's account of the Great Depression.
Hansen helped create the United States Social Security system in 1935 and assisted in drafting the Full Employment Act in 1946, which established the Council of Economic Advisors. He also served as special economic adviser to Marriner Eccles at the Federal Reserve Board from 1940 to 1945.
Hansen's secular stagnation thesis, developed in the late 1930s, held that the American economy would never grow rapidly again because the historical drivers of growth, including technological innovation and population growth, had been exhausted. He argued that only large-scale, ongoing deficit spending by the federal government could prevent permanent stagnation. The thesis was controversial and appeared undermined by the economic expansion that began in 1940.
Paul Samuelson and James Tobin were among the students who attended Hansen's famous Harvard seminar on fiscal policy, and both went on to win the Nobel Prize in Economics. Samuelson credited Hansen's 1938 book Full Recovery or Stagnation? as the primary inspiration for his own multiplier-accelerator model of 1939.
Alvin Harvey Hansen was born on the 23rd of August 1887 in Viborg, South Dakota, the son of a farmer named Niels Hansen. He died on the 6th of June 1975 in Alexandria, Virginia, at the age of 87.