The French population has seen several shifts or interruptions in trends during the last decades. These have had a knock-on effect on the assumptions and results of population forecasts regularly produced by INSEE. At the start of the 1980s, all available data pointed to a fairly rapid halt in the growth of the French population: a fall in fertility, a sharp reduction in migratory flows, a slowdown in life expectancy gains. This prospect of a turnaround in the population gradually faded during the following thirty years. Population ageing has, for its part, ben confirmed over time even if the discourse on the causes of this ageing has, for its part, evolved slightly. The predominant effect of longer life expectancy has been reaffirmed over successive forecasting exercises.