Obviously there's no way to actually count people who are trying to hide. But there hasn't been a huge increase in Border Patrol staffing, so an increase in encounters likely indicates an increase in illegal immigration. They only catch a fraction.

Or do you have an alternate hypothesis that fits the data?

> While the number of encounters was the highest on record last fiscal year, the number of individuals encountered was considerably lower. That’s because more than a quarter of all migrant encounters at U.S. borders in both fiscal 2021 and fiscal 2020 (27% and 26%, respectively) involved repeat crossers, according to CBP statistics. By comparison, the proportion of repeat border crossers was much lower in the 2019 fiscal year (7%), before the Border Patrol began regularly expelling migrants during the coronavirus outbreak.

This evidence runs exactly contrary to both the "open border" and "unprecedented numbers" theory and indicates a change in policy that directly explains the new numbers.

No, the evidence supports that we effectively have a (mostly) open border. Illegal immigrants who make it through the border are usually not expelled immediately. Many are processed and released pending some kind of further action. This can stretch out for years, especially if they claim asylum (even without evidence to justify the claim).

> Illegal immigrants who make it through the border are usually not expelled immediately. Many are processed and released pending some kind of further action. This can stretch out for years, especially if they claim asylum (even without evidence to justify the claim).

And yet the quote I just gave says the increase is due to people being removed from the country and trying to get back in.