[1][2] His paternal family were Protestants from Nîmes who were exiled in Geneva, Switzerland after the repeal of the Revocation of the Edict of Nantes in 1685.
[3] His paternal great-grandfather, also named Louis Say, moved first to Amsterdam, where he was a member of the Walloon Church, before settling in Geneva in 1694.
[1][3] After the government changed the law on tariffs in 1814,[1] Say switched to using sugarcane in 1815.
[5] In 1832, with Constant Duméril, Say also opened a beetroot sugar factory in Ivry-sur-Seine, known as the "Raffinerie de Jamaïque" (English: "refinery from Jamaica").
[6] Partly in reaction to his brother, Say became an economist at the age of forty-four, after he had become wealthy.
[1] Contrary to classical liberals, he was in favour of tariffs as a way to encourage production.