Lots of editorials and opinion pieces about how the low birth rate in the United States argues for increasing immigration. Such as:
“According to the National Center for Health Statistics, the number of births in the United States in 2020 was down 4% from the previous year. This marked the sixth year in a row that births have declined and amounts to the lowest number of births in the country since 1979….The U.S. economy depends on growth of the labor force to generate the tax revenue needed to maintain programs like Social Security. And a key component of labor-force growth is immigration.” (From here.)
About 50% of new immigrants are employed or readily employable. The implicit message is that immigration must shift towards a higher percentage. This is difficult because workers often have families. Also, because temporary work programs, for those with or without a lot of formal education, are hard to manage. Nonetheless, the simple demographic argument for more immigrants is easy to understand.
A piece on birth rate trends since 1960 and how to measure the birth rate is here.