Purchase to Plate National Average Prices (PP-NAP)

The datasets (described below) used to build PP-NAP are USDA’s What We Eat in America (WWEIA), the dietary component of the National Health and Nutrition Examination Survey (NHANES), the USDA Food and Nutrient Database for Dietary Studies (FNDDS), the Information Resources, Inc. (IRI) retail grocery scanner data, and the Purchase to Plate Crosswalk (PPC). The generalized process for construction of the national average prices is as follows:

1. Select USDA food codes representing foods or beverages that were reported 10 or more times in the WWEIA cycle, or are needed for the Thrifty Food Plan (TFP) market basket update.

2. Review recipes in the FNDDS of the selected foods to determine whether recipe modifications are needed to accommodate convenience foods and include standard substitutions in the recipe.

3. Calculate the total purchase weight sold and expenditure for each item in the IRI data.

4. Link scanner data Universal Product Codes (UPCs) (barcodes) to food codes in the USDA nutrition databases using the PPC.

5. Convert purchase weight to edible weight for each UPC using the PPC conversion factors.

6. Sum the total expenditure and edible weight across UPCs for each USDA food code.

7. Calculate the average price per 100 grams of the USDA food codes by dividing expenditure by edible weight.

8. Apply average unit prices for the USDA food codes to the recipes identified in step two and calculate the unit price of the FNDDS foods selected in step one.

The resulting prices are nationally representative of foods reported eaten by WWEIA/NHANES participants. The resulting price for any particular food may be derived from multiple brands and private labels, package sizes, flavors, and types. The IRI grocery scanner data represent individual products as purchased in a grocery store. The WWEIA/NHANES codes and supporting recipes in the FNDDS are more general (e.g., BBQ sauce versus a brand-specific BBQ sauce).

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