OK, 1st question is: what is the mathematical definition of a generation?
Obviously by this list (I have seen it before), there is no defined time range! That's ridiculous in itself.
20 years MITE be an acceptable average range for a generation. Altho since we're so communicative in the last century, we often define ourselves more narrowly - by decades.
To me, the average generation-length ("gestation", if you will) is 30 years - but that's considering how old you are having children, how old your mom & dad were, how old your grandparents were, etc, all when they had children. Which muddles it, cuz people are having kids all the time.
I don't like this method! Let's just go back to naming decades, not naming ethereal "generations" of varying scope!
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.