The lowest level Census
geographical identifier for which data is included in the major
public Census files (e.g., STF3a). The blockgroup is an area that
includes several street blocks.
Census place
A Census geographical
identifier roughly corresponding to a city or town.
Census tract
A Census geographical
identifier that groups several blockgroups.
MCD
Minor civil division. A Census unit of
aggregation formally called ``County Subdivision (Census).'' MCDs
are typically smaller than counties, and larger than
VTDs. However, a single VTD may overlap several
MCDs. MCDs are Census summary level 060; MCD codes are stored in
the Census variable COUSUBCE. When MCDs are not well defined, we
use the Census County Division (CCD), but for simplicity continue to
refer to them as MCDs.
MCD Group
A geographical identifier constructed by
the ROAD Project on the basis of county, MCD, and
VTD geographical identifiers from the PL94-171 Census
data. An MCD Group is never bigger than a county and never smaller than
an MCD. An MCD Group includes multiple MCDs up to the point where no
PL94-171 VTD contained in any of the MCD Group's MCDs overlaps into an MCD
not contained in the MCD Group. For more information on the
creation of MCD Group units, see
the section on plvdkey.exe.
PL94-171
A set of files produced by the
U.S. Bureau of the Census, containing just
demographic variables on race at a variety of levels of aggregation,
including the VTD or Census precinct.
precinct
A usually contiguous
geographical area in which the adult citizens are assigned a single
voting booth to cast their election ballots. In some states it is
called an ``election district.'' Occasionally several physical
voting booths exist within one precinct. The
precinct-level electoral data files which constitute the central
element of the ROAD datasets have this as their unit of
observation.
precinct-level electoral data
Information on a wide variety of
electoral variables, including voting registration,
registration-by-party, turnout, and voting tallies for each party in
federal, state, and local elections. The precinct-level electoral data files cover the
years 1984 through 1990 and are at the precinct level.
ROAD Project
The Record of American Democracy
project.
STF3a
A set of files produced by the
U.S. Bureau of the Census,
containing 3,727 demographic and socioeconomic variables at the
state, county, MCD, place, and
blockgroup levels of aggregation.
VTD
Voting District (or Voter Tabulation District).
A Census geographical label roughly corresponding to a
precinct. VTD-level data are typically
only available in Census PL94-171 files. Since precincts are defined
locally, a Census VTD is in some cases just an approximation of the
actual voting precinct. Four states (Kentucky, Mississippi,
Montana, and Oregon) did not participate in the Census PL94-171
Program, in which the precinct-VTD correspondence was made tighter;
these states do not have any VTD definitions. Eight other states
participated in only a limited capacity (Texas, North Carolina, and
others), and thus have VTD definitions only in some counties. VTDs
are PL94-171 summary level 700; VTD codes are stored in the PL94-171
variable SAC3.
