Training at Ecole Polytechnique (Paris, 1962-64), Expert Démographe (Institut de Démographie, University of Paris I, 1966) and Doctorat d’Etat (PhD) in Economics, (University of Paris I, 1972)
First position at INED (Institut national d'Etudes Démographiques, Paris) in October 1965. Visiting lecturer, University of Pennsylvania, Philadelphia (Sept. 1974 - June 1975). Head of the Department on sociodemography at INED, 1979-1992. Head of the Inserm-Ined-Univ.Paris XI Unit (U569: Epidemiology, Demography and Social sciences) from 2000 to 2006. Director of the Elfe project (French national Child Birth Cohort) 2005-2010. Associate Professor at the Collège de France, 2008-2009. Currently Emeritus Research Director at Ined
Main fields of research: Human Reproduction (fertility, sterility, contraception, Assisted Reproductive technologies); sexual Behaviour in the context of AIDS; family structures (couple formation and dissolution, cohabitation...); and population dynamics.
In 2000-01, HL chaired a Working Group preparing a Report on Research on Ageing for the French Ministry of Research. More recently, as a Correspondant member of the French Academy of Sciences, he has prepared a Report on Population, Climate and Food, in relation with the Chair held at the College de France in 2008-09 on Sustainable Development.