PRB has produced an updated series of tables and maps identifying neighborhoods with a very high risk of undercounting young children in combination with low 2020 Census self-response rates. As of September 3, the average self-response rate in census tracts with a very high risk of undercounting children under the age of 5 was 59%, while the mean self-response rate in tracts with a low risk of undercounting young children—or a potential net overcount—was much higher, at 72%. The mean response rate across all census tracts in the United States was 65%.
You can access the tables and maps here. To view the maps, download the google document and open the downloaded html.