Originally Posted by
orbitmic
I'm only basing it on media articles as I don't have access to that data, but if it is mistaken, then it is a mistake shared across multiple sources. See here for a reference (section starting: "la ligne 7 est la mieux desservie"):
Cinq faits à connaître sur le métro parisien Rough translation: "with 60 trains an hour at peak time, line 7 is the best equipped. Line 13, often criticised by public transport users reaches 52 trains an hour. This, however, is a lot more than the 4 trains an hour of line 3b."
And here:
Les petits secrets de la RATP révélés au public L'interconnexion n'est plus assurée mentioning 60tph for line 7 and 59tph for line 9.
Sometimes these stats are given as total trains calling at the station (i.e. in both directions).
The other thing that happens (both in London and elsewhere) is that operators can provide extra peak capacity in a single direction for very short periods, sometimes just for a single hour. This can make comparisons between networks tricky.