Current techniques for census adjustment involve the "synthetic assumption" that undercount rates are constant within "post-strata" across geographical areas. A poststratum is a subgroup of people with given demographic characteristics; poststrata are chosen to minimize heterogeneity in undercount rates. This paper will use 1990 census data to assess the synthetic assumption. We find that heterogeneity within poststrata is quite large, with a corresponding impact on local undercount rates estimated by the synthetic method. Thus, any comparison of error rates between the census and adjusted counts should take heterogeneity into account.
"Heterogeneity and Census Adjustment for the Intercensal Base." Statist. Sci. 9 (4) 476 - 485, November, 1994. https://doi.org/10.1214/ss/1177010260