Jules Regnault
1834–1894 (age 60)
Biography
Jules Augustin Frédéric Regnault (French: [ʁəɲo]; 1 February 1834, Béthencourt – 9 December 1894, Paris) was a French stock broker's assistant who first suggested a modern theory of stock price changes in Calcul des Chances et Philosophie de la Bourse (1863), using a random walk model. A key conclusion appears on Page 50: "l'écart des cours est en raison directe de la racine carrée des temps", in English: "the deviation of prices is directly proportional to the square root of time". He is also one of the first authors who tried to create a "stock exchange science" based on statistical and probabilistic analysis. His hypotheses were used by Louis Bachelier.