That they are approximately the same size. There was an assumption that you know how populous these cities are, but to to be clear, roughly the same administrative area (Geneva Ave or so North vs everything within the Périphérique) has a population of 865k for SF and 2,244k for Paris.

Next someone will say, "But Paris doesn't have to worry about earthquakes". Then you reply with a map of Tokyo.

There are an endless supply of rebuttals to the idea that a place could be more dense than it really is. They’re almost entirely provably false, but that’s not the point: they come from people who don’t like the implication, and they’ll grasp at any straw they can find.

Or more perniciously, to stoke up anti-immigrant sentiments.

Ah yea thanks, didn’t know population for either of top of my head.