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NHGISJOIN
Linking key to county-level data in the NHGIS project

Description

NHGISJOIN is a county identifier that can be used to match IPUMS data with the county-level boundary files and aggregate data from the National Historical Geographic Information System (NHGIS). The corresponding variable in NHGIS is called "GISJOIN2."

Researchers can use this variable to match IPUMS data with NHGIS boundary files (to make maps) or to match NHGIS county-level data with IPUMS microdata (to facilitate multi-level analysis). For user convenience, copies of the NHGIS boundary files are available on the IPUMS County Codes page. NHGIS aggregate data are available via the "Data Finder" link on the front page of the NHGIS homepage.

Codes

This variable is only available from 1850-1930. NHGISJOIN is a 7-digit numeric county identifier that can be used to match IPUMS data with the county-level boundary files and aggregate data from the National Historical Geographic Information System (NHGIS). The corresponding variable in NHGIS is called "GISJOIN2". Researchers can use this variable to match IPUMS data with NHGIS boundary files (to make maps) or to match NHGIS county-level data with IPUMS microdata (to facilitate multi-level analysis). For user convenience, copies of the NHGIS boundary files are available on the IPUMS County Codes page. NHGIS aggregate data are available via the "Data Finder" link on the front page of the NHGIS homepage. NHGISJOIN 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 by Census year (and data sample if specified).

NHGISJOIN Specific Variable Codes

User Note: A small number of cases in IPUMS cannot be matched to the NHGIS. These are coded as 9999999 in NHGISJOIN. These were non-county areas such as Indian reservations and military installations. There were 6 such counties in 1900 and 1 in 1910.
A small number of counties in NHGIS also cannot be matched to the IPUMS. In all cases, these were very small counties that were not captured by the IPUMS sampling procedures. All of these counties contained fewer than 1,000 people; many were administrative areas with no population at all. There were 9 such counties in 1850, 56 in 1860, 32 in 1870, 33 in 1880, 2 in 1900 and 1910, and none in 1920 and 1930.

Comparability

NHGISJOIN is year-specific. Codes can have different meaning depending on the census year. Researchers should be careful to match IPUMS and NHGIS data only from the same year.

NHGISJOIN is only available from 1850-1930. From 1940 to the present, IPUMS only identifies a limited number of counties (due to confidentiality restrictions).

Universe

  • All households and group quarters.

Availability

United States
  • 2016: --
  • 2015: --
  • 2014: --
  • 2013: --
  • 2012: --
  • 2011: --
  • 2010: --
  • 2009: --
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  • 2002: --
  • 2001: --
  • 2000: --
  • 1990: --
  • 1980: --
  • 1970: --
  • 1960: --
  • 1950: --
  • 1940: --
  • 1930: All samples
  • 1920: All samples
  • 1910: All samples
  • 1900: 5%; 1%; 1.2% ovrsmp
  • 1880: All samples
  • 1870: All samples
  • 1860: All samples
  • 1850: All samples
Puerto Rico
  • 2016: --
  • 2015: --
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  • 2013: --
  • 2012: --
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  • 2005: --
  • 2000: --
  • 1990: --
  • 1980: --
  • 1970: --
  • 1930: --
  • 1920: --
  • 1910: --

Flags

This variable has no flags.

Editing Procedure

There is no editing procedure available for this variable.