That's more than any other age group in the country.
Torsten Slok, an economist at Deutsche Bank and the author of a new report on these echo boomers (or millennials or Gen-Yers, whichever you prefer), believes their widespread presence matters a great deal.
Just as baby boomers began spending like crazy in 1980s and 1990s, today's 20-somethings are poised to do the same in the mid-2020s.
"What's important from a broader perspective is they're about to get married and have children within the next five years," Slok says.
Marriage and family aren't the only characteristics that define echo boomers, who were born roughly between 1985 and 1995. Many of them grew up with financial constraints that have affected where they live, what they buy, and how they feel about important issues.
Here's what America's largest generation is all about.