A couple of factors: Back in olden times, before Douglas Coupland applied the Generation X moniker in 1991, they used to talk about the Baby Bust generation. The Baby Boom was when all of the GIs got back from the war and all started getting jiggy at the same time. Then, the birth rate dropped significantly. In my elementary school, we had combined grades 2/3, and grades 4/5, because there weren't enough kids enrolled for full classrooms otherwise.
Also, the Baby Boom generation is defined as 1946 to 1964, which is 19 years, compared to the 16 years of what we call Generation X now, from 1965 to 1980.
Granted, is not a huge difference—71 million Boomers and 73 million Millennials vs. 64 million Gen X—but there's fewer of us. But also, the name and the generational categories are pretty recent developments. When Coupland's book came out, I was too young to be Gen X, the people he was writing about were adults out into world. I wasn't part of the classic Gen X disaffected-slacker culture, and its touchstones don't really resonate with me. It wasn't until years later that the definition of Generation X definitively included me. That's why you'll often see a lot of younger Gen X identify with the Xennial label, because we have a lot more in common with "elder Millennials," which makes the whole cohort less cohesive.
It's almost like the generational cutoff years are arbitrary, and that society changes continuously, and not in discrete jumps. It's almost like, too, that something unspeakably neo-liberal happened in 1980, and the real division is between the people who came of age before they pulled up the ladders to prosperity behind themselves (Boomers and older Gen X) and the people who came of age after (Xennials, Millennials, and so on). Nevermind, sorry, that's just some anti-capitalist hogwash. /s
