This is from Neil Howe at Lifecourse.com:
We ran these number per Census as of July of this year for everyone age 18+. They are cut exactly according to our birthyear boundaries:G.I. (born 1901-1924), 4.5 millionSilent (born 1925-1942), 26.2 millionBoomer (born 1943-1960), 65.6 millionGeneration X (born 1961-1981), 88.5 millionMillennial (born 1982-200?) 18+, 52.0 millionTotal: 236.8 million.Subtract this from the current total U.S. pop (around 311.8 million) gives you 75.0 million under age 18. That’s about 4.2 million per cohort, which is just under the recent birth per year totals. Again give a bit of allowance for immigration. So that fits.Also, nearly 2/3 of these cohorts under age 18 are Millennials, which gives you nearly 100 million total Millennials–so that fits. The remaining 25-30 million are Homelanders.