Using recent Census data, 25 is the most common age for Americans in 2016. These young adults are not alone, as ages 22, 23, 24, 26, and 27 earned the remaining top six most common ages.
This is to say that the Millennial generation is large, according to Calculated Risk. Six years ago, Baby Boomers accounted for the most common ages. In 2010, 50 was the most common age, and 49 was the second-most common.
Baby Boomers, however, will continue to remain a large force as they age. U.S. residents age 65 and over grew from 35 million in 2000 to 49.2 million in 2016.