The famous British medical journal predicts a decline in the world’s population as early as 2100, which would be a first since the Black Death of 1347. Of course, demographers are not soothsayers and their analyses are based on hypotheses and algorithms that may vary according to economic variables, but current trends seem to show an acceleration of the demographic transition in many countries of the South and an accelerated ageing of the population in the countries of the North and in emerging countries. China could reach its historical population peak as early as this year. Is this a risk for the financing of our economic and social model or an obligation to reinvent ourselves?