Mostly flat from 2010-2021, with a recent uptick to 131 million. The discrepancy is likely due to the boomers aging out of the category, and a smaller generation coming in.
Let me put it another way: the [20, 25) and [25, 30) age cohorts are larger than any cohort aged 50+ that might have recently aged out. So that "prime age" workforce is still growing.
This could be true, but it isn't obviously true (to me). (I dispute a little bit the idea that there are many new workers in the [25, 30) demo.) There are 37M workers 55+, but only 20M in the 16-24 range: https://www.bls.gov/cps/cpsaat18b.htm (2024 numbers)
Nobody in either of those cohorts is in the BLS "prime age" group which is [25, 55). The incoming cohorts that are now 15 to 25 are larger than the outgoing cohorts that are 45 to 55.
Growing up to an estimated 342 million.
It also has an estimate for the working population (ages 25-54, so called "prime workers"): https://fred.stlouisfed.org/series/LNU00000060
Mostly flat from 2010-2021, with a recent uptick to 131 million. The discrepancy is likely due to the boomers aging out of the category, and a smaller generation coming in.