The Congressional Budget Office makes a new population forecast (revising one in 2024, here) which says that without immigration, the country’s population will begin to decline in 2033. A revised rate of population growth generally slows over the next 30 years, from an average of 0.4% a year between 2025 and 2035 to an average of 0.1% a year between 2036 and 2055.  This is due in part a lower of the fertility rate from 1.75 noted in the 2024 forecast to 1.6 on the long run. Net immigration, projected at 1.1 million a year, becomes an increasingly important source of population growth period without immigration, the population would shrink beginning in 2033.

This forecast makes immigration, which is more concentrated in working ages than the existing population (due to fewer children coming in), even more important in the growth of the working population. The prime age (25-54) population has been declining since about 2020. Only with immigration, which I have estimated addd 600,000 persons to the workforce, is the working age population increasing.

More detail:

The CBO estimates that pre-Biden the net immigration rate was about 920,000 per year. After three explosive years under Biden, when net immigration averaged 2.9 million (most of humanitarian parole and asylum applicants), and two last years averaging 1.75 million, the CBO projects for 2027 – 2055 at 1.1 million immigratns. This 1.1 million estimate, like past ones, are the sum of a complex sorting out of new and revised legal status, netting out to a round number of the net number of persons from abroad expected to live here indefinitely.