For directions on reading the variable description see Data Dictionary Introduction.

Availability: 
 

1850	1860	1870	1880	1900	1910	1920	1940	1950	1960	1970	1980	1990
X	X	X	X	X	X	X	X	X

Universe: 
All households and group quarters. 

Description: 
SEA stands for State Economic Area, a concept described fully in Donald J. Bogue, State Economic Areas, (Washington D.C., 1951). SEAs are generally either single counties or groups of contiguous counties within the same state that had similar economic characteristics when they were originally defined prior to the 1950 census. 

The census first used SEAs in 1950 and the concept was applied retroactively to the 1940 sample. We constructed SEAs for 1850-1880, 1900, 1910, and 1920 for the IPUMS by combining counties to match as closely as possible the components of the 1940-1950 SEAs. However, shifts in county boundaries, primarily resulting from the creation of new counties as populations shifted and grew, mean that these earlier SEAs do not always contain exactly the same territory as their 1940-1950 counterparts (see COUNTY). This is particularly true of areas with relatively small populations in earlier years which generally had more unstable county boundaries. There are exceptions, of course. Users who need to know the precise boundaries of counties for earlier years can refer to the boundary files available from Geoscience Publications; see COUNTY for information. 

For 1940 and 1950, SEAs with fewer than 100,000 residents were combined to form SEAs exceeding 100,000 residents, in order to meet confidentiality requirements. The resulting SEAs were applied to the previous census years. 

The 1950 census did not create SEAs for Alaska and Hawaii; the IPUMS assigns them each a single, separate SEA value for those samples that contain these states (see STATEICP). Furthermore, for 1900, we did not attempt to fit Indian lands in what later became Oklahoma into the SEAs unless they were clearly part of a particular county in 1900. Military reservations in 1900 and 1910 are also coded separately from the SEAs that contained them. Although West Virginia did exist as a state in 1850, SEAs that later became West Virginia are coded in all years as West Virginia. Finally, in all years, 1850-1920, a few SEAs were unidentifiable. These SEAs are coded as missing within the state that contained them. 

The component counties of each SEA are detailed in "Geographic Tools" in Volume 2: User’s Guide Supplement. 

Comparability: 
The county components of the 1940 and 1950 SEAs are the same. For previous years, SEA boundaries differ only insofar as county boundaries shifted. 

Keep in mind that the SEA boundaries, first created for the 1950 census, are based upon the economic characteristics of counties at that time. Counties within a particular SEA may or may not have been as economically homogeneous in previous years. But SEA may still be useful for identifying geographical units smaller than states and larger than counties. 

SEA has some similarities to the IPUMS variables CNTYGP97 and CNTYGP98, which are available for 1970 and 1980. 

Flags: QCOUNTY 

Codes: 
See "Geographic Tools" in Volume 2: User’s Guide Supplement for SEA codes.