Documentation
Overview
The Quarterly Food-at-Home Price Database (QFAHPD) is constructed from household food-at-home purchase data from Nielsen Homescan data. The report, On the Accuracy of Nielsen Homescan Data (see link below), contains information on household-level purchases of both Universal Product Code (UPC) foods—most packaged and canned food—and random-weight (non-UPC) items such as fresh fruits or vegetables. See:
On the Accuracy of Nielsen Homescan DataERS created the food groups to correspond with the 2005 Dietary Guidelines for Americans and to capture price premiums for convenience and processing. ERS researchers aggregated the food purchases to estimate household-level quarterly prices for over 50 food groups. The household-level prices were then aggregated to estimate quarterly market-level prices. Prices are presented in dollars per 100 grams of food as purchased by consumers. See:
Methodology Behind the Quarterly Food-at-Home Price DatabaseTwo Versions of QFAHPD
The original version of the Quarterly Food-at-Home Price Database (QFAHPD-1) contains prices for 52 food groups based on both UPC-coded and random-weight food purchases. Quarterly prices are available for:
- 26 metropolitan markets for 1999-2006, and
- 9 nonmetropolitan areas for 2002-2006 and 4 nonmetropolitan areas for 1999-2001.
A second version of the Quarterly Food-at-Home Price Database (QFAHPD-2) contains prices for 54 food groups based on only UPC-coded food purchases. Quarterly prices are available for:
- 26 metropolitan and 9 nonmetropolitan markets for 2004-2010.
- A redefined carbonated nonalcoholic beverage group, which now excludes diet versions of beverages.
- Two new food groups: 1) diet carbonated beverages, and 2) unsweetened coffee and tea. Dry weights for coffee and tea have been converted to liquid equivalents, assuming that 2 grams of dry tea leaves and 10 grams of dry coffee yield 180 ml of liquid beverage.
Since 2007, Homescan data have included less detailed information about random-weight food items so that these purchases could not be incorporated into estimates of prices for food groups that include random-weight items. Because random-weight items are often priced quite differently than UPC-coded items, prices for 2007 and after are not comparable with prices for earlier years for food groups with random-weight items. The QFAHPD-2 was therefore developed using only UPC-coded purchases for the years 2004-2010, and prices are constructed consistently across those years.
Revisions
Minor changes were made to both the QFAHPD-1 and QFAHPD-2 for 8 food groups (for all years) that include random-weight purchases. For the QFAHPD-1, minor changes were made for all food groups in 1999-2001 that include random-weight purchases. These changes were necessary to incorporate corrections made to the raw Homescan data. See the Read Me tab in the Excel data files for more information.
Resources
Methodology Behind the Quarterly Food-at-Home Price Databaseprovides an indepth discussion of how the QFAHPD database was constructed, along with basic findings about food price variation across geographic areas and price differentials within food groups between markets.
Codebooks are available for researchers and others to analyze the data and conduct research. Use Codebook-1 for QFAHPD-1 and Codebook-2 for QFAHPD-2. Users can download the data by clicking on the spreadsheet for the specific food group.