Issue: Each year, the United States Department of

Agriculture estimates the number of people eligible to participate in the Special Supplemental Nutrition Program for

Women, Infants, and Children (WIC), the number who

will likely participate, and the expected cost of food.

These estimates are used in developing budget requests for

WIC, which is funded by appropriations law on an annual

basis. If the number of people eligible and likely to participate in WIC is underestimated, the result is a shortage of

funds available to fully serve them. If the number of WIC

eligibles and participants is overestimated, an inefficient

allocation of funds across programs occurs. Estimation of

eligibility and participation is a complex process, due to

data limitations, varying State program eligibility criteria,

and alternate definitions of key variables. 

Background: WIC provides supplemental food, nutrition

education, and referrals to health care and other social

services to low-income women, infants, and children who

are at nutritional risk. The number of WIC participants has

increased dramatically since the program began in 1974.

In fiscal 2002, a record 7.5 million persons per month participated in the program, at a cost to taxpayers of over

$4.3 billion. The increase in the number of participants

has been largely the result of increased congressional

funding as well as cost-containment measures (fig. 1).

To qualify for WIC, applicants must meet categorical,

income, and nutrition risk eligibility requirements. 

(1) Categorical eligibility. A WIC applicant must be: a

pregnant woman, a nonbreastfeeding woman up to 6

months postpartum, a breastfeeding woman up to 1 year

postpartum, an infant under 1 year of age, or a child up to

his/her 5th birthday. 

(2) Income eligibility. The family income of WIC applicants must be at or below 185 percent of the Poverty

Income Guidelines ($33,485 for a family of four in July

2002). Applicants who participate or who have certain

family members who participate in the Food Stamp,

Medicaid, or Temporary Assistance for Needy Families

(TANF) programs, are adjunctively income eligible, that

is, they are deemed to meet the income eligible criteria

automatically.

(3) Nutrition risk. Applicants must be at nutrition risk, as

determined by a health professional. Federal regulations

recognize five major types of nutrition risk for WIC eligibility: (1) anthropometric risk (e.g., underweight or overweight); (2) biochemical risk (e.g., low hemoglobin or low

hematocrit); (3) medical risk (e.g., diabetes mellitus); (4)

dietary risk (e.g., failure to heed Dietary Guidelines for

Americans recommendations); and (5) predisposing factors (e.g., homelessness).

United States

Department of

Agriculture

Economic 

Research

Service

Food Assistance and Nutrition Research Report Number 34-3 July 2003

WIC School

meals

CACPF General

Figure 1. Average number of WIC participants per 

month, fiscal years 1974-2002

Millions

Source: Food and Nutrition Service,USDA.

1974 76 78 80 82 84 86 88 90 92 94 96 98 00 02

0

1

2

3

4

5

6

7

8

Children

Infants

Women

Estimating Eligibility and

Participation in WIC

Food Assistance Research Brief

Victor Oliveira, victoro@ers.usda.gov, (202) 694-5434

James Blaylock, jblayloc@ers.usda.gov, (202) 694-5402
2 Economic Research Service / USDA

Estimating Eligibility and Participation in WIC / FANRR-34-3

Findings: Estimating the number of eligibles who meet

each of the three eligibility requirements, in practice, is

difficult and complex. For example, although women are

categorically eligible for WIC for their entire pregnancy,

they are not likely to know that they are pregnant immediately. For the purposes of estimating eligibility, it is not

clear if a pregnant woman should be considered categorically eligible at conception or when her pregnancy is confirmed. Data indicate that over half of all pregnant women

in WIC enrolled when they were at least 4 months pregnant.

Once the issue of categorical eligibility is resolved, methods for determining income eligibility must be established.

Many issues immediately surface. For example, the

income eligibility of individuals is based on the size and

income of their “family” or “economic unit.” However, the

definition of what constitutes a family varies among the

local WIC agencies that determine applicants’ eligibility.

Another issue concerns the time frame for measuring

income. WIC State agencies may consider either an applicant’s income during the past year or the applicant’s current income, whichever one better reflects the applicant’s

status. Since income may vary considerably during the

year (for example, income might drop during the birth of a

child) estimates based on annual income will differ from

those using a shorter period such as a month. Estimating

income eligibility is also complicated by WIC adjunct eligibility with Medicaid enrollment. Income eligibility for

Medicaid varies by State, with some State programs

allowing participation with incomes greater than 185 percent of poverty, such as 275 percent in Minnesota. 

The final step in estimating WIC eligibility is to determine

the number of income-eligible people who are at nutritional risk. This task is complicated by the fact that there are

about 70 different criteria that can be used in determining

nutritional risk. If applicants meet any one of the criteria

they may be considered at nutritional risk. In practice, few

income-eligible persons fail to meet at least one of the criteria. 

Once the number of persons who are fully eligible for

WIC has been estimated, the number of those eligible persons who would actually participate in the program must

be estimated. Since little is known about WIC participation, food stamp participation rates in the past were used

as proxies for WIC participation rates. However, because

eligibility rules, target population, benefits, and degree of

stigma differ between the programs, participation rates

likely also differ. 

Summary: In the first stage of a three-step project funded

by the Economic Research Service (ERS) and administered by the Food and Nutrition Service (FNS), Mathematica Policy Research, Inc., prepared a background

report that for the first time reviewed the current methodology used to estimate the number of persons eligible for

and participating in WIC. In the second stage, the National

Research Council convened an expert panel that identified

a number of factors that make estimating eligibility and

participation in the WIC program uncertain. In the third

stage of the study, the panel will examine alternative methods and data sources for estimating the number of persons

eligible for WIC and those who are likely to participate if

the program was fully funded. The final report from stage

three is due summer 2003. 

Information Sources:

Mathematica Policy Research, Inc. Estimating the Number of People

Eligible for WIC and the Full-Funding Participation Rate: A Review of

the Issues. February 12, 1999.

National Research Council, Committee on National Statistics, Division

of Behavioral and Social Sciences and Education. Estimating Eligibility

and Participation for the WIC Program: Phase 1 Report. 2001.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex,

religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET

Center at (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 14th and Independence Avenue,

SW, Washington, DC 20250-9410, or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.