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 2007 Census Publications

  Congressional District Methodology

The Census of Agriculture, conducted every five years, is the leading source of facts and statistics about the Nation's farms and ranches and the only source of uniform, comprehensive agriculture data for every state and county, or county equivalent, in the U.S. Following each census, reporting farms and ranches are assigned to congressional districts and two products are prepared, district profiles and district rankings. For 2007, the congressional districts are for the 110th Congress.

Purpose and Tabular Presentation

Congressional district profiles provide data on selected farm, economic, and operator characteristics for the farms and ranches assigned to the district. Seven states have only one congressional district, Alaska, Delaware, Montana, North Dakota, South Dakota, Vermont, and Wyoming. For these "at large" states, the state total is presented for the district. Profiles are not available for those districts with very little agriculture reported, if any, to protect the confidentiality of individual reports.

The 2007 profiles include comparable values from the 2002 Census of Agriculture (108th Congress). Users should beware that some redistricting has occurred between censuses. Maine and Pennsylvania redistricted for the 109th Congress. Georgia redistricted for the 110th Congress. Texas redistricted for the 109th Congress and again for the 110th Congress. For many of these districts, the change is very small and the 2002 data are included. For those districts with significant changes, the 2002 data have been withheld by replacing them with "NA".

The ranking of congressional districts presents the order of districts from largest to smallest for selected items from the 2007 Census of Agriculture. The statistics presented in this report include:

  • Operator characteristics
  • Farm characteristics
  • Selected value of agricultural products sold
  • Selected livestock and poultry inventories
  • Selected crops area harvested

How Farms were Assigned to Congressional Districts

The 110th Congress congressional district tabulations of 2007 Census of Agriculture data are based on the location of the operations.  Census respondents are asked to declare their principal county of operation as the county with the greatest share of their total value of production.  Additionally, the operator’s zipcode is known, however, this zipcode does not necessarily relate to the location of the farm or ranch.  The congressional district assignments were based on county/state-level flat files and digitized cartographic files provided by the Census Bureau, the federal agency responsible for congressional apportionment among the states, as well as for mapping the resulting congressional districts in accordance with state requests.  An additional source for congressional districts was a Postal Service product, the Address Information Systems (AIS) Zip + 4 database, whose records link a district to a zip5 value (or values) and to an associated zip4 interval, for the last four digits of zip9s containing the record’s zip5 and falling within the record’s congressional district.

Of the 1,523,825 farm and ranch reports returned for the 2007 Census, 83.6 percent could be deterministically assigned to a congressional district because the operation’s reported principal county fell entirely within a congressional district.  Another 12.9 percent of the total farm and ranch records could be assigned with certainty to a congressional district because their mailed zipcode (zip5 or zip9) was located in the operation’s principal county and the zipcode fell entirely in a single congressional district.  Thus, deterministic assignments, those made with complete certainty, were achieved for 96.5 percent of the records.  The remaining 3.5 percent of Census farm and ranch records had to be assigned probabilistically following a statistical model.  For these cases, probabilistic assignment models were developed for each county divided into two or more districts.  The probabilities of assignment to each congressional district within the county were the proportion of the county’s digitized agricultural land contained in the district as maintained by NASS.  All probabilistically assigned large farms and ranches were reviewed by NASS Field Offices to verify their assignments and, in some cases, corrections were made.

All farm counts and totals released in these products are fully adjusted for nonresponse and coverage.


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