Prominent Personalities - Ivo Lah

Ivo Lah (1896–1979) was a Slovene mathematician, actuary, statistician and demographer. During the First World War he fought as an Austro-Hungarian soldier against Italy, and after the war against Austria in the struggle for the northern border

He studied in Vienna and Zagreb and became one of the leading actuaries in the Balkans. From 1937 to 1940 he published in Ljubljana the first Yugoslav journal of actuarial science, Glasnik Udruženja aktuara Kraljevine Jugoslavije, which also featured mathematical articles in Slovene. In 1942 he published the first mortality tables, while in 1947 he published in Zagreb a trilingual monograph on the numerical foundations of life insurance, which served as background documentation for the negotiations on war reparations as a member of the state delegation, he took part in the negotiations in Rome. In 1954 he introduced the numbers that were soon named after him, which connect rising factorials with falling ones and which, together with Stirling numbers, form a triangle linking rising, ordinary and falling factorials. Although Lah numbers originated in actuarial research, they soon found a place in discrete mathematics, where they remain the subject of intensive study. The fact that the author of these famous numbers was a Slovene only became clear in 2002. Lah’s obscurity is attributed to a stigma that followed him until his death: records show that he was deprived of voting rights after the liberation.

Tomaž Pisanski