The effects of residential geocode on distance estimation and determination of closest facility. PANEL 1 shows that in some cases, the ZIP Code center is much closer to representing the geography of the sampled locations than the ZCTA centroid, although the effect on distance estimation may be negligible. PANEL 2 illustrates that respondents may be comparably close to multiple service centers. Use of ZCTA centroid or ZIP Code center geocode alone may result in different determinations of which facility is closest. A probabilistic sampling approach includes all facilities to the degree that they are relevant.