I recently started using IPUMS ACS to calculate internal migration. I calculated 1 year region to region migration for population aged 1+, excluding within region migration. When I compare my results to the MOVERS BETWEEN REGIONS (2015 American Community Survey 1-Year Estimates) table from FactFinder, I see that they are close to each other but not exactly the same. For example, acording to my calculations 96,654 people moved from Midwest to North East while FactFinder reports 91,687 movers.
Any idea why there is about 5,000 people difference?
I first thought the IPUMS ACS sample may not be the whole sample but it lists more than 3.1 million observations.