About population estimates using one-year ACS data

I was trying to calculate the total population for each race group using one-year ACS data from 2001 to 2019. I used the weight perwt in calculating the population, but could not get a close number as what reported in Census website (for example, for year 2019, it is reported here: https://data.census.gov/cedsci/table?q=B02018&tid=ACSDT1Y2019.B02018). Then, I tried to figure out why this happened by calculating the total population for the whole country to see if the number can be matched. Even for this, my estimates seem to be quite different from the real number. I got the total population 230,076,328 using one-year ACS 2019 and the STATA code: bysort year: egen pop=total(perwt), which is far away from the Census number 328.3 million. The difference is obviously beyond the normal error. I re-downloaded the ACS 2019 data. Without making any changes to the data, I found the total number of observations is 2,257,409. Given that one observation represents about 100 people, I guess I should have had more than (or around) 3 million observations in ACS 2019. I do not know in which part I got it wrong. Thank you for your help.

I ran the same exact command on the 2019 ACS and got a value of 328,200,000. Please make sure that when you create your extract that you select “Rectangular (person)” as your data structure and that the “Select Cases” and “Customize Sample Sizes” fields are left unused. Please let me know if after confirming these extract specifications you still encounter problems. I didn’t find an IPUMS account associated with your forum email address, but if you could send an email from the address associated with the account to ipums@umn.edu I can take a look at the extract from our end.

Dear Ivan,

Thank you so much for the detailed explanation. Indeed, I re-used a previous extract as the basis for defining the new extract, and did not notice that the previous extract has a age restriction (selected age groups between 16 and 70). I just removed the age restriction and found that number could be matched to the Census reports. Thank you so much for your help. Really appreciate it.

Best,
Wenjian