The population of Descartes in central France increased by upwards of 150% from 1962 to 1968 after a general negative trend over the preceding seventy years. Why was this? All I can find is that the town changed its name from "La Haye-Descartes" to simply "Descartes" in 1967. I'd assume it has some relation to the population growth, probably a result of a small town of ~1,700 being flooded with ~2,600 new residents.
Based on this page from the French School for Advanced Studies in the Social Sciences, it appears that the neighbouring Balsesmes merged into La Haye-Descartes in 1966, before the combined commune was renamed to Descartes the next year.
In 1962, the two communes had remarkably similar population levels of 1,679 and 1,689. With a combined population of 4,267 in 1968, the growth rate was only 26.7%. Still high, mind you, but not the shockingly stratospheric 154% that it initially appears.
2Thought as much, but couldn't track it down. Good work. Jan 22, 2018 at 5:59
4Confirmed by a governmental website: "01/01/1967 : Haye-Descartes devient Descartes suite à sa fusion avec Balesmes." insee.fr/fr/metadonnees/cog/commune/COM37115-descartes– EvargaloJan 22, 2018 at 9:57
3One thing that maybe isn't obvious to non-French speakers; "commune" is just their word for "town". It doesn't imply anything special about its political structure outside of that (like it would in English).– T.E.D. ♦Jan 22, 2018 at 14:40
13So ..., it was a Cartesian join? Jan 22, 2018 at 16:32
3@Steph - I think you misunderstand. In the US at least, a "commune" would imply a group of unrelated people living together essentially under a Communist governing system. Likely in the same building or compound of buildings, and pooling all labor, income, and often possessions. Most of them tend to be either religious (cults), or run by (ex?) Hippies. My point being the French word "commune" probably should be translated into an appropriate English term.– T.E.D. ♦Jan 22, 2018 at 21:23
I'd assume it [the name change] has some relation to the population growthI certainly wouldn't. I would look for A) how does this population change compare to that of France as a whole B) some new industry being stablished (or an old one flourishing) or C) new infrastructure making it easier to move to/from nearby economic centers.
The Chevènement law tidied up all these practices, abolishing some structures and creating new ones. In addition, it offered central government finance aimed at encouraging further communes to join together in intercommunal structures. Unlike the only partially successful statute enacted in 1966 and enabling urban communes to form urban communities, or the more marked failure of the Marcellin law of 1971, the Chevènement law met with a large measure of success, so that a majority of French communes are now involved in intercommunal structures.