Created in 2008, the annual Sustainable Development - Environment, Energy and Society Chair is supported by TOTAL.
Henri Leridon's main areas of research concern human reproduction (fertility, sterility, contraception), population dynamics, sexual behavior in the context of AIDS, and the family (conjugal situations - marriage, cohabitation, etc., and family structures). - and family structures).
His early work focused on analyzing the fertility of human populations, following in the footsteps of Louis Henry's research into the various components of fertility(fertility, intra-uterine mortality, post-partum sterility and permanent sterility) and the means of recombining them in models, in particular using microsimulation methods (Monte-Carlo). These analyses, which make it possible to establish the link between the physiological constraints of human reproduction and the effect of individual behaviours, are initially based on data collected on non-contracepting populations, most often populations of the past, which were in a situation of natural fertility. But the major advantage of reproductive modelling is that it can also incorporate the effects of various birth control methods, and establish - for example - relationships between the number of contraceptive couples, the effectiveness of the techniques used and the drop in fertility. Reliable information on the practices of contemporary populations is therefore essential, and this can only be obtained through surveys: Henri Leridon has directed several national surveys and collaborated on several international projects. Today, the postponement of the first birth to an increasingly later age is raising concerns about its possible consequences for couples (difficulty in obtaining the desired children) and for the overall level of fertility, consequences that can be analyzed using the same models.
The study of population dynamics lies at the heart of demography. In the context of low fertility in developed countries since the end of the twentiethcentury , as in that of still strong demographic growth, it is not possible to set just any objective for demographic evolution: for example, Henri Leridon has shown that maintaining a strictly constant size for the French population over a long period would only be possible at the cost of wide oscillations in fertility. He also showed that recourse to immigration was not a solution to ageing populations. Finally, plans to reform several scientific academies gave him the opportunity to study the demographic evolution of these particular bodies (the Academy of Sciences of the Institut de France and the Academy of Medicine), and to examine their development prospects according to various operating hypotheses. This study has led to several international collaborations on the subject.
Changes in fertility rates in Western countries are often linked to changes in family structures and norms. These changes are all the more significant in that they concern what is still considered one of the essential foundations of the organization of our societies, and a safe haven in difficult times: the family. In this field, we have had to innovate in terms of observation methods (current statistics were becoming insufficient) and sometimes in terms of concepts. Surveys organized by Henri Leridon at INED have enabled us to monitor and better understand these changes.
Finally, an often neglected component of reproductive behavior is sexual activity. In the context of the HIV-AIDS epidemic, it has become essential to have reliable data on current sexual behavior. But it is essential to assess the reliability and sincerity of the answers obtained, particularly with regard to the intensity of sexual activity and the number of partners. Henri Leridon took part in two major French surveys, in 1992 and 2005, and analyzed in particular the problems of consistency in data on the frequency of intercourse and the number of partners, estimated over several periods.
