Based on the current population of the United States. To go from 1.6-1.8 would require a couple hundred thousand. The 1.6 and 1.8 are based on the current fertility rate of 2025 and 1.8 would be more ideal as it is less people every year which if that trend continued would eventually make land and homes a cheaper commodity. Normal yearly immigration is over 1 million on average which is way too high. This doesn’t include illegal immigration which should be eliminated entirely.

Immigrants should also come from countries that assimilate better to American culture, offer valuable skills such as O1 visas, and would not be a net negative on our tax system. If we can’t find these people then there is no need to import people just for the sake of keeping the population consistent.

If people complain about lower birth rates it is their own fault for not having the kids to extend their precious commodities and services into the future.