From personal observations, on the Paris-Grenoble line a few years ago ; when the train is empty, and 2nd class remains cheaper than 1st (weekdays evening), the social divide is well marked, and the 1st class reads Le Figaro, whereas when the train is almost full, as on a weekend, the 2nd class overflows into the 1st, and you find Libé readers there...

Un roi sans divertissement est un homme plein de misères