It doesn't really "slip pretty quickly", it slips over the course of many generations. The average is close enough that extreme cases can be sorted into outliers. My definition still very clearly describes people growing up in different historical eras the same as the other does, it simply takes away the self-identification privileges that these other commenters prefer.
The average really isn't close enough that you only need to consider outliers.
Two generations of 30 year old first time mothers fit into the same time as three generations of 20 year old first time mothers.
Neither of those cases is an outlier, and that's slip in only two/three generations.
Oh wow only three generations and it now overlaps slightly less than the vast majority of people, sounds like an outlier.
It doesn't really "slip pretty quickly", it slips over the course of many generations. The average is close enough that extreme cases can be sorted into outliers. My definition still very clearly describes people growing up in different historical eras the same as the other does, it simply takes away the self-identification privileges that these other commenters prefer.
The average really isn't close enough that you only need to consider outliers.
Two generations of 30 year old first time mothers fit into the same time as three generations of 20 year old first time mothers.
Neither of those cases is an outlier, and that's slip in only two/three generations.
Oh wow only three generations and it now overlaps slightly less than the vast majority of people, sounds like an outlier.