Dear Joey,
For the 2010 Summary File 2, the Census Bureau uses suppression when there are fewer than 100 people identifying as a specific detailed race/ethnicity group in a specific geographic unit. Thus, while there were a certain number of Asian Indians in the entire US, not all census tracts contained 100 Asian Indians. When there were fewer than 100 Asian Indians in a census tract, the Bureau suppressed the Asian Indian count for that tract. The specific text from the Bureau’s technical documentation is:
The presentation of SF 2 tables for any of the 331 population groups is subject to
a population threshold of 100 or more people. That is, if there are fewer than 100 people in a specific
population group in a specific geographic area, their population and housing characteristics data are not available for that geographic area in SF 2
When you sum the Asian Indian count for census tracts, the nationwide total will be reduced because of suppression.
Essentially, the census tracts you have data for are those with more than 100 Asian Indians, but you don’t have data for all Asian Indians in the US.
Sincerely,
Dave