Joseph Clemént Juglar, 1819-1905, was, as his compatriot François Quesnay, a physician turned economist. In 1862 he published his masterpiece “Des crises commerciales et leur retour périodique en France, en Angleterre, et aux États-Unis” in which he analysed economic crises in France, England and the United States from a monetary perspective. He explained that periods of inflation and expansion are concluded when the central banking system contracts money supply. Although he was not the first to analyse and explain crises from such a point of view, he provided new ideas and perspectives.
Juglar was able to identify economic cyclical trends that helped develop the business cycle theory. He identified a medium economic cycle of between 7 and 11 years of duration, the so-called Juglar cycle. In this cycle one can identify trends in the investment levels and in unemployment.