SERIAL is an identifying number unique to each household record in a given sample. All person records are assigned the same serial number as the household record that they follow. (Person records also have their own unique identifiers - see PERNUM.) A combination of YEAR, DATANUM, and SERIAL provides a unique identifier for every household in the IPUMS; the combination of YEAR, DATANUM, SERIAL, and PERNUM uniquely identifies every person in the database.
For 1850-1930, households that are part of a multi-household dwelling can be identified by using the DWELLING and DWSEQ variables. See "Sample Designs" for further discussion of sampling from within multi-household dwellings.
SERIAL is an 8-digit numeric variable which assigns a unique identification number to each household record in a given sample (See PERNUM for the analogous person record identifier). A combination of YEAR, DATANUM, and SERIAL provides a unique identifier for every household in the IPUMS; the combination of YEAR, DATANUM, SERIAL, and PERNUM uniquely identifies every person in the database. SERIAL specific variable codes for missing, edited, or unidentified observations, observations not applicable (N/A), observations not in universe (NIU), top and bottom value coding, etc. are provided below if applicable by Census year (and data sample if specified).