Millennials are now 83 million strong -- one quarter of the US population. Because the number of Boomers is shrinking over time, Gen Y has overtaken them.

From June 2015, we learn that Millennials are also much more diverse than the 75 million remaining baby boomers:

Millennials, or America’s youth born between 1982 and 2000, now number 83.1 million and represent more than one quarter of the nation’s population. Their size exceeds that of the 75.4 million baby boomers, according to new U.S. Census Bureau estimates released today. Overall, millennials are more diverse than the generations that preceded them, with 44.2 percent being part of a minority race or ethnic group (that is, a group other than non-Hispanic, single-race white).

These latest population estimates examine changes among groups by age, sex, race and Hispanic origin nationally, as well as in all states and counties, between April 1, 2010, and July 1, 2014.

Even more diverse than millennials are the youngest Americans: those younger than 5 years old. In 2014, this group became majority-minority for the first time, with 50.2 percent being part of a minority race or ethnic group.

Reflecting these younger age groups, the population as a whole has become more racially and ethnically diverse in just the last decade, with the percentage minority climbing from 32.9 percent in 2004 to 37.9 percent in 2014.

By comparison there are roughly 66 million in Gen X:

http://www.pewresearch.org/fact-tank/2015/01/16/this-year-millennials-will-overtake-baby-boomers/

Note that these numbers from Pew are rough estimates. 

Like... that is one confusing graph, man. How can there be an INCREASE in the numbers of "people born between 1981 and 1997"... after 2014?!?!

New college students and immigrants?

Goldman Sachs Millennials infographic is excellent:

http://www.goldmansachs.com/our-thinking/pages/millennials/

2500 Reddit comments:

https://reddit.com/r/Futurology/comments/40m9cv/millennials_infographic/