I imagine it depends on how closely you model the conditional probabilities.
If it gets down to correctly modeling the probability of colon cancer diagnosis by age, sex and ZIP code, and also the correct distribution of ages by ZIP code, then that'll be a potential problem in counties that only have one male 87-year-old.
I'm talking specifically about modeling iid/non-iid sequences of data from events, experiments, etc. Haven't read the paper so, I'm not sure if I'm talking past the authors or OP.
