Yes, or as we used to call it back in the day "empirically".

Plus, it doesn't matter if it happens as much or more in some backwater third world country.

It's already enough of a problem that among first world countries the US is quite a pain in the ass airport control.

Heck, it's enough of a problem that it feels like a pain in the ass. It wont be less of a problem if per capita e.g. Belgium or Albania are worse...

There isn't data on this. This incident likely wasn't logged in any way. CBP is a rogue agency and the least transparent. They don't respond to FOIA anymore either.