Economists - Irving Fisher (1867-1947)
As with many Classical economists, Fisher had a varied background. He was born in New York State in 1867 and his first specialism was mathematics. He graduated from Yale with a BA in maths, but then he turned to economics, gaining a PhD, and was very influential in a variety of areas. One particular area was his development of index numbers - a mathematical technique that is invaluable in economics. Index numbers that we use today include the FTSE index to measure share values and the RPI to measure inflation.
He also wrote about and campaigned for world peace, healthy eating and a healthy lifestyle and was often regarded by his colleagues as something of an eccentric. His influence waned towards the end of his career, but he left behind a legacy of theory that is still very important to us. Much of the Classical and Monetarist theory of inflation is based on his (Fisher) Equation of Exchange .