With Baby Boomers/Xers (Baby Bust) and Ys (Echo Boom) it's sort of easy since it all has to do with the Birthrate. Though no one can agree whether the echo boom began in 1976 or 1982. I kind of lean toward the 1975 cut off year for Xers.
Obviously by this list (I have seen it before), there is no defined time range! That's ridiculous in itself.
I guess they are going by Shared experiences.
I don't like this method! Let's just go back to naming decades, not naming ethereal "generations" of varying scope!
That doesn't help either, For example the teenagers in 1970 were still Hippies where as teenagers in 1979 were Disco queens. So when you describe the 70's generation which is it?
Until people start having kids only in the first or last few years of a decade and none during the rest there is really just no way to really come up with a good definition or range of a generation.
My HS years were 72-75. I guess that makes me part Hippie and part Disco. Maybe I'm a "Dippy", LOL.
I am not a statistician, so I cannot fully appreciate the extent to which the demographic studies go, but I have never thought those particular polls/data to be representative of what I understood to be happening when I decided to take note of what was going on...and that wasn't really until I was aware that I was going to be a part of that society pretty soon...that usually takes up to about 20 years for a person.
I'd say the generational thing needs to take more into account than statistical data from national census.
High School Class of '80 - my pop music > punk, wave, rap, metal, country ...... other music > Classical, classic jazz (not new age!), etc