Absolutely no one.. none.. know what is coming over the border. We do not control it.. we do not know via aircraft or boots on the ground. The number of illegal aliens crossing? The Border Patrol tells us they catch about one in three. They are not fully.. fully funded and they work eight hours a day just like human beings. The Administration uses computers to determine how many are crossing, and that clearly means they are counting about 1/3rd of the actual number which make the administration and their counters.. very dangerous fellows.
Do they create jobs? Who knows. Prominent journalists are calling the Congressional Budget Office non-partisan and I don't believe that at all.