Despite those generous child allowances in France, and much better childcare facilities than in the UK- most French families remain small. France does have an ageing population- with huge parts in the centre which are practically abandonned, bar Brits, Germans, Dutch and Swiss- and some French families coming back for holidays to the house they've inherited from parents.
Here in Switzerland immigrants tend to integrate well, as well as keep their cultural centres and friendships. And I am sorry to say, it is the British and American expats, concentrated in Zurich, Zug and Geneva area- who tend to integrate the least- not learn the language, attend their own clubs and activities, their own Churches- and this for many over decades. I take no pleasure in saying this.