(CNN) — Here’s a look at five generations of Americans in the 20th century: the “Greatest Generation” (or GI Generation), the “Silent Generation,” baby boomers, Generation X and millennials. In order to examine economic trends and social changes over time, demographers compare groupings of people bracketed by birth year. There are sometimes variations in the birth year that begins or ends a generation, depending on the source. The groupings below are based on studies by the Census, Pew Research and demographers Neil Howe and William Strauss.
The “Greatest Generation” (or GI Generation) Born in 1924 or earlier.
Tom Brokaw coined the term the “Greatest Generation” as a tribute to Americans who lived through the Great Depression and then fought in WWII. His 1998 bestselling book, “The Greatest Generation,” popularized the term.
John F. Kennedy, born in 1917, was the first member of the “Greatest Generation” to become president. Lyndon B. Johnson, Richard M. Nixon, Gerald R. Ford, Ronald Reagan, Jimmy Carter, and George H. W. Bush were also born between 1901 and 1924.
The “Silent Generation” Born 1925-1945 (Sometimes listed as 1925-1942).
A 1951 essay in Time magazine dubbed the people in this age group the “Silent Generation” because they were more cautious than their parents. “By comparison with the ‘Flaming Youth’ of their fathers & mothers, today’s younger generation is a still, small flame.”
The Silent Generation helped shape 20th century pop culture, with pioneering rock musicians, iconic filmmakers, television legends, beat poets, gonzo journalists and groundbreaking political satirists.
No members of the Silent Generation have served as president.
As of 2015, there were between 22.4 million and 29.8 million Americans in this age group, depending on whether the generation ends with the birth year 1942 or 1945.
Baby Boomers Born 1946-1964 (Sometimes listed as 1943-1964)
Baby boomers were named for an uptick in the post-WWII birth rate.
At the end of 1946, the first year of the baby boom, there were approximately 2.4 million baby boomers. In 1964, the last year of the baby boom, there were nearly 72.5 million baby boomers. The population peaked in 1999, with 78.8 million baby boomers, including people who immigrated to the United States and were born between 1946 and 1964.
Bill Clinton was the first baby boomer to serve as president. George W. Bush and Barack Obama are also baby boomers. Donald Trump and Hillary Clinton are too.
According to the Census, the baby boom began in 1946 but demographers Neil Howe and William Strauss, authors of the groundbreaking 1991 book, “Generations: The History of America’s Future,” argued that the baby boom began as a social and cultural phenomenon with people who were born in 1943.
As of 2015, the number of baby boomers ranges from 74.9 million to 82.3 million, depending on whether the generation begins with the birth year 1943 or 1946.
Generation X Born 1965-1980 (Sometimes listed as 1965-1979)
“Class X” was the name of a chapter in a 1983 book, “Class: A Guide Through the American Status System,” by historian Paul Fussell. Novelist Douglas Coupland used the term as the title of his first book, “Generation X: Tales for An Accelerated Culture,” published in 1991.
No members of Generation X have served as president.
As of 2015, the number of Generation X-ers ranges from 61.5 million to 65.8 million, depending on whether the generation ends with the birth year 1979 or 1980.
Millennials Born 1981-1997 (Sometimes listed as 1980-2000; the range of birth years for millennials may be updated as further demography studies about this generation are conducted, according to Pew Research).
Howe and Strauss introduced the term millennials in 1991, the year their book, “Generations,” was published.
In 2014, the number of millennials in the United States eclipsed the number of baby boomers, according to the Census Bureau. The Census counted approximately 83.1 million millennials, compared with 75.4 million baby boomers. Millenials represent one quarter of the nation’s population. The Census also reported that millennials are more diverse than previous generations, as 44.2% are part of a minority race or ethnic group.
More than 32% of millennials lived at home with their parents in 2014, according to a Pew Research study. Young men were more likely to live with a parent than a spouse or domestic partner, with 35% living with parents and 28% living with spouses or partners. It’s a reversal from 1960, when about 56% of young men lived with spouses or partners while 23% lived in their parents’ homes.
2016 was the first year any millennial was eligible to run for president (since the minimum age is 35).
As of 2015, the number of millennials ranges from 75.4 million to 92.3 million.
Post-Millennials? What’s Next? The next generation of children and teens younger than millennials has not been formally named by demographers yet.
As of 2015, the number of people in this age group ranged from 61 million to 73.6 million.