Jules Regnault

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.

During the first years of his life, Jules Regnault lived in the département du Nord (France) where his father worked.

When his father died on 16 January 1846 in Paris, his family moved to Brussels, where Odilon, Jules’ brother, became a writer and a student at the Université Libre de Bruxelles in advanced mathematics.

In all likelihood, when Jules and Odilon arrived in Paris, their financial resources were limited, forcing them to live in one (or two) garret room(s), for which no tax had to be paid.

According to his Calcul des chances et philosophie de la bourse, the only valid investment should be bonds, which is precisely what his inventory shows.