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Table 2 U.S. examples for using the Probabilistic Sampling Method (PSM) for distance estimation

From: A probabilistic sampling method (PSM) for estimating geographic distance to health services when only the region of residence is known

Region of known residence (p) Smaller areas within the region for which demographic data is available (q) Typical ratio (q/p)
county Zip Code, census tract, township, block group, census block Can vary widely from 36:1 for rural counties to 1000:1 for metropolitan counties.
Zip Code Census tract, census block group, census block From 10:1 to 10,000:1
Census tract Census block group, census block Variable; 50:1
Census tract 94 Meter grid population data for the U.S. (LandScan U.S.A.) Highly variable: 1000:1