Largeness would be my guess.

Overheard in the Office:

Harvard MBA student: So, are you flying back tonight? What airport are you flying into? New York?

Suit: Why would we fly to New York? We're from Philadelphia.

Harvard MBA student: I didn't know Philadelphia had an airport.

Suit: It's the fifth-largest city in the U.S., of course it has an airport.

Harvard MBA student: Largest city? Based on what?