The geographic unit is the geographic level to which individual data is aggregated.
A. Census
1. Block- Blocks are the smallest geographic unit utilized by the SWDB. The Census Bureau designates new census blocks every ten years. There are over 400,000 census blocks in the state. The designation for block is BL.
2. Tract- Census tracts are larger geographic units, also created by the Census Bureau decadently. A tract is made up by a collection of blocks. There are over 5,000 census tracts in the state. The designation for tract is TR.
B. Precincts- Precincts are a geographic unit utilized by County Registrars of Voters and the Secretary of State as part of the registration and voting process. Precinct boundaries change with each election. Thus, precincts from one election to another are not comparable. There are five different types of precincts utilized by the Statewide database.
1. RR, RG- Two designations for registration precincts. Registration precincts are the aggregate unit for the Statement of Registration (SOR, see below) and are used to collect information about registered voters. There are approximately 30,000 registration precincts, the exact number of which varies from election to election. The RR precinct is imported directly from the county registrars; the RG precinct is normalized for computational purposes. On the SWDB site you will find registration data by RG precinct from 1992, 1996 and 1998 general elections and 1998 and 2000 (incomplete) primaries.
2. SS, SV- Two designations for voting precincts. Voting precincts are the aggregate unit for the Statement of Vote (SOV, see below) and are used to collect data from a given election. There are approximately 40,000 voting precincts, varying from election to election. The Statewide database has no data aggregated to SS precinct; the adjusted SV precinct is the reporting unit for SOV data. Data are available by SV precinct from 1992, 1994, 1996, and 1998 general elections and 1998 and 2000 (incomplete) primaries.
3. SR- The SR precinct is a special geographic unit created to allow comparison of SV and RG precincts. It is thus not a direct correlate of any registrar's precincts, but rather a unit constructed to facilitate the examination of registration and voting data by the same geographic unit. The Statewide Datbase has SOV and REG data arranged by SR precinct (which, like other precincts changesfrom election to election) for 1992, 1994, 1996, 1998 general elections and 1998 primary election. We also provide, as an intermediate step in the merging process, past elections aggregated to a recent SR precinct. Currently you will find all elections above merged to 1998 SR precincts.
C. Changing between Geographic Units- It is possible, in some cases, to change from one geographic unit to another. It is usually possible to change from a unit of smaller or comparable size to a larger or comparably sized unit; but not from a large to a smaller unit. This is done through the utilization of a conversion file. Typically, these files contain a field with the original geographic unit, a second field with the new geographic unit, and a third field with the percentage overlap. To locate a conversion file, click on DATA, then on a geographic coverage and then click the link CNV. To change geographic units, first match the file organized by the original geographic unit and match it to the conversion file. The multiple each variable by the percentage in the conversion file. Finally, aggregate the variables by the new geographic unit.