WASHINGTON — Princeton-based Mathematica Policy Research was selected by the U.S. Department of Agriculture’s Economic Research Service to conduct a major survey on food choices and expenditures by U.S. households — the National Household Food Purchase and Acquisition Study (N.H.F.P.A.S.).

"Helping American families improve their overall health is one of my top priorities," said Tom Vilsack, Secretary of Agriculture. "This ambitious, five-year effort will fill in critical gaps in existing data on the food purchases of U.S. households and be invaluable in assessing and enhancing the effectiveness of U.S.D.A.'s food assistance programs for low-income families."

Unique, detailed data not previously available to researchers will be gathered by the survey, Mr. Vilsack claimed. E.R.S. will use the resulting data to study how food assistance programs and other economic and demographic factors affect household food-purchase decisions and health outcomes. This effort will be carried out with the support of U.S.D.A.'s Food and Nutrition Service, the agency relayed.

"For the first time, researchers will have data that captures key factors like food prices, where food is purchased, dietary knowledge and the interplay of food assistance programs and food choices," said Rajiv Shah, Under Secretary for Research, Education, and Economics at U.S.D.A.

E.R.S. recently led a study on the problem of limited access to nutritious food — a study requested by Congress in the 2008 Farm Bill. The study addressed "food deserts," or areas with little or no access to retail outlets providing healthful food. The new U.S.D.A. food purchase survey will enable E.R.S. to further analyze how lack of access and retail outlet choice and location influence households' food purchases and dietary quality.

The results of this survey will allow U.S.D.A. to understand how households make their purchase choices, and what those choices mean for diet quality.

Data from the Mathematica survey can be used to address issues including:

• how price and income influence food choices and the dietary quality of food purchases;
• what participants in the S.N.A.P., formerly the Food Stamp Program, buy and how much it costs;
• how participation in food assistance programs influences food purchases;
• the relationship between food purchase decisions and levels of food security (consistent access to sufficient food for a healthy lifestyle); and
• how access and retail outlet choice and location influence food purchases and the resulting dietary quality of purchases; and the influence of nutrition knowledge on food purchases.

For the N.H.F.P.A.S., Mathematica will collect data from all members of sample households on foods acquired and purchased from all sources, including foodservice establishments. Particular attention will be given to representing low-income households in the data collection.