How do I know who counts as a "resident" for the American Community Survey (ACS)?
The ACS uses the concept of "current residence" to determine who should be considered residents of sample housing units. The basic idea behind this concept is that everyone who is currently living or staying at an address for more than two months is considered a current resident of that address.
This means that their expected length of stay is more than two months, not that they have been staying in the housing unit for more than two months at the time when the survey is conducted. Persons away from their residence for two months or less, whether in the United States or overseas, on a vacation or on a business trip, are considered to still be a "resident" at the address, and the unit is classified as occupied and eligible for inclusion in the survey. Persons away from their residence for more than two months are considered not to be a resident. For the ACS, if no one is determined to be a current resident in the sampled housing unit, it is classified as "vacant."
There are a few exceptions to the "two-month" rule, as noted below:
Persons Without Another Place to Stay -- Anyone staying at a residence who does not have another place to stay, even if they are at the residence for two months or less, are always considered current residents of the residence.
Children Away at School -- Children (below college age) who are away at boarding school or summer camp for more than two months are always considered current residents of their parents' homes. College students' current residency is established by the two-month rule.
Children in Joint Custody -- Children who live under joint custody agreements and move between residences are always considered current residents of the sampled housing unit where they are staying at the time of the interview.
Residency in Group Quarters facilities is determined differently. All people residing in the selected facility at the time of interview, regardless of the length of stay, are eligible to be selected to be interviewed in the ACS.
For more information on ACS residency rules, read Chapter 6: Survey Rules, Concepts and Definitions, Section 6.3: Residence Rules on the Methodology page of the ACS website.