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So How Many Millennials Are There in the US, Anyway?

US Population by Age Group June 2 2021

Gen Z is certainly a new darling for marketers, but there’s still plenty of attention paid to Millennials. Their lives are deconstructed on many different levels, from their use of social media to their outlook on the retail industry and their family lives. Those analyses are all helpful in their own right, but – stepping back to the big picture for a moment – how many of these prized individuals are there in the US? The most recent data out from the Census Bureau gives a sense of how large this coveted generation is.

Before putting out some numbers, there are a few problems to take note of. Chiefly, there is no consensus definition of a Millennial; while 18-34 seems to be the most commonly used bracket, other studies might use an 18-29 range or some other, making it necessary to identify age ranges when referring to this cohort.

Another issue? Consider this. If a 2010 study defined Millennials as being aged 18-34, shouldn’t the same study this year define them as being aged 29-45? Somehow the 18-34 age range stays fixed despite the passage of time…

Meanwhile, it’s also worth noting that most Millennials don’t even identify as Millennials, and a young Gen Xer might feel more culturally similar to Gen Y. In other words, cultural and behavioral tendencies don’t tend to have fixed age breaks. (That’s why many argue that it’s more useful to look at personas rather than age brackets.)

Nevertheless, things being the way they are, marketers and researchers often look at age brackets. So here’s a reference list of some commonly used age brackets and their corresponding population estimates and population shares as of July 1st, 2020 (the most recent data available).

  • 12-17: 25.1 million (7.6%) [pop share flat]

  • 18-24: 30.0 million (9.1%) [pop share down]

  • 25-34: 46.1 million (14.0%) [pop share flat]

  • 35-44: 42.1 million (12.8%) [pop share up]

  • 45-54: 40.4 million (12.3%) [pop share down]

  • 55-64: 42.4 million (12.9%) [pop share flat]

  • 65-74: 32.5 million (9.9%) [pop share up]

  • 75+: 23.1 million (7.0%) [pop share up]

Some other popular age groups, including the ever-present 18-34 bracket:

  • 18-29: 53.3 million (16.2%) [pop share down]

  • 18-34: 76.1 million (23.1%) [pop share down]

  • 18-49: 138.2 million (41.9%) [pop share down]

  • 35-49: 62.1 million (18.8%) [pop share down]

  • 50-64: 62.8 million (19.1%) [pop share down]

  • 50+: 118.5 million (36.0%) [pop share flat]

  • 55+: 98.1 million (29.8%) [pop share up]

  • 65+: 55.7 million (16.9%) [pop share up]

Want an Excel file showing population estimates by single year of age and gender? We’ve formatted the data for you and made it available for download here.

A couple of fun facts to leave with:

  • As of July 1st last year, there were an estimated 104,819 centenarians (100+) in the US, a number that continues to grow each year. Some 79,772 – or 76.1% – of them were female; and

  • There were more males than females for each single year of age from newborn through age 37, but then more females than males for each single year of age from 38 onwards (with the lone exception being 40). The biggest disparity in favor of males was for 27-year-olds (117,108 more), while for females it was for 73-year-olds (233,385 more).

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