I see that 3.3 USAnians visited France last year, but I'm having trouble finding the number of Brits who did.
textibule, a "known unknown" isn't a safe bet. It's something that you know you don't know. The number of Brits who visited France last year is for me a known unknown.
For a friend of mine, the fact that a pangolin walks on its hind legs was an unknown unknown until the other day. She had never heard of pangolins, so she didn't know that she didn't how their manner of locomotion.

