Can anyone explain (or link to an explanation) of the ACS special population detailed tables?
As far as I can tell, they have the same data as the regular detailed tables, but for fewer geographies.
For example, https://data.census.gov/table?g=040XX00US29$0500000&d=ACS+5-Year+Estimates+Detailed+Tables&tid=ACSDT5Y2021.B01001 shows detailed table B01001 for all counties in Missouri. But, the same table from the "special population" set (https://data.census.gov/table?g=040XX00US29$0500000&tid=ACSDT5YSPT2021.B01001) omits counties with a total population less than about 7,000.
I'm not having much luck of the Bureau's site.