Luke pointed out some other potential divergence points, such as departure rates (death/emigration). There’s also the potential issue that the subset queried may be divergent from the population as a whole; as a non-descriptive example, male college students may have a lot of sex with female non-college students, and female college students strictly have sex with male college students; if you’re querying college students, you could get largely divergent numbers.
But if your numbers are largely divergent, they’re probably wrong.
Well, assuming equal populations, anyway.
Luke pointed out some other potential divergence points, such as departure rates (death/emigration). There’s also the potential issue that the subset queried may be divergent from the population as a whole; as a non-descriptive example, male college students may have a lot of sex with female non-college students, and female college students strictly have sex with male college students; if you’re querying college students, you could get largely divergent numbers.
But if your numbers are largely divergent, they’re probably wrong.