Office of Analysis, Nutrition, and Evaluation

WIC Program Coverage: 

How Many Eligible Individuals Participated in the 

Special Supplemental Nutrition Program for Women, 

Infants, and Children (WIC): 1994 to 2003? 

Recently, the method used to calculate the 

number of individuals eligible for the WIC program 

was evaluated and an improved methodology was 

developed. These new, improved estimates provide better insight on the WIC program and should 

help improve the program in the future. The new 

estimates show that 13.5 million individuals were 

eligible for WIC and 7.7 million participated in WIC 

in 2003. This coverage rate of 57% is consistent 

with trends since 2000 and is similar to the coverage rate found in the Food Stamp Program. 

Eligibility Versus Participation 

WIC is a discretionary grant program, not an 

entitlement program, so enrollment in WIC depends on funding levels. Consequently, accurately 

estimating the number of people eligible for WIC 

benefits is very important. If the number of people 

eligible is underestimated, there could be funding 

constraints or waiting lists to serve eligible people. 

If the number of people is overestimated, it may 

unnecessarily limit appropriations to other programs. Knowing how many people are eligible 

also informs outreach activities, allowing WIC staff 

to target scarce resources effectively. 

Estimates of Eligible Population Have 

Improved 

In the past, the number of infants and postpartum women enrolled in the program exceeded the 

number estimated to be eligible by 20 to 30%. This 

raised questions about whether ineligible people 

were enrolled in the program or whether the estimates were wrong.

The Food and Nutrition Service (FNS) of the 

USDA recognized the need to improve these estimates and undertook a series of studies to improve 

the methodology. FNS commissioned studies that 

included a review of the nutritional risk criteria used 

in WIC eligibility, an examination of income variability among WIC participants, and a study to 

summarize the issues involved in estimating WIC 

eligibility. Ultimately, FNS asked the Committee on 

National Statistics of the National Research Council to review the old methodology and develop an 

alternate. 

The old methodology used the March Income 

Supplement of the Bureau of the Census’ Current 

Population Survey (CPS) to estimate the number of 

infants and children who live in families with annual 

incomes below 185% of the poverty guidelines. The 

evaluation of the old methodology found that it failed 

to fully reflect current eligibility rules and regulations. 

Among its many short-comings is that it only partially 

accounted for those who are adjunctively eligible for 

WIC based on their enrollment in the Medicaid, Food 

Stamp, or Temporary Assistance to Needy Family 

(TANF) programs. Additionally, the old methodology 

did not account for changes in monthly income, 

which can have an impact on eligibility, especially for 

women who are pregnant or post-partum and may 

have fluctuations in income around the time of birth 

of their child. The old methodology also did not 

make any adjustment to the distribution of infants 

and children in the data from the CPS, so it overestimated the number of children while underestimating 

the number of infants that were eligible. 

The Committee concluded that it would be most 

effective to focus on the estimation issues that 

seemed to have the largest overall impact on the 

number of people eligible for WIC. For this reason, 

the following issues were the center of the revised 

methodology: accuracy of the CPS in counting all 

infants and children; adjunctive eligibility through 

TANF, Food Stamp, and Medicaid programs; use of 

monthly income versus annual income to determine 

income eligibility; adjustment for 6-month certification 

What is WIC?

The Special Supplemental Nutrition Program for 

Women, Infants, and Children, commonly known as 

WIC, is a Federal grant program to States to provide 

food and nutrition education benefits and referral services to low-income pregnant and postpartum women, 

infants, and young children. 

To be eligible for the WIC program, individuals must 

meet income guidelines, a State residency requirement, 

and be individually determined to be at “nutrition risk” by 

a health professional. 

To be eligible based on income, applicants’ income 

must fall at or below 185 percent of the U.S. Poverty 

Income Guidelines. A person who participates or has 

family members who participate in certain other benefit 

programs, such as the Food Stamp Program, Medicaid, 

or Temporary Assistance for Needy Families, automatically meets the income-eligibility requirement. 
Office of Analysis, Nutrition, and Evaluation Page 2 

periods; alternative definitions of household units; 

and the number of individuals who are at nutritional 

risk among those who are income eligible. 

Summary of New Methodology

The Committee on National Statistics of the 

National Research Council developed two strategies to estimate the number of individuals eligible 

for WIC. One strategy continues to use the CPS 

for annual estimates of the eligible population, but 

suggests improvements over the old methodology. 

The other strategy uses the Bureau of the Census’ 

Survey of Income and Program Participation 

(SIPP), a survey that is based on a continuous series of national panels designed to capture labor 

force, program participation, and monthly income 

data. 

CPS Estimation 

There are both advantages and disadvantages 

of using data from the CPS for estimating the number of people eligible for WIC. One of the biggest 

advantages is the regular and timely release of the 

CPS data. It also has a large sample ensuring that 

there are enough infants and children on which to 

base eligibility estimates. The CPS also has many 

questions related to income sources and participation in other government programs. 

The main disadvantage of the CPS is that it 

does not measure monthly income flows, which 

could result in substantial underestimation in the 

number of people eligible for WIC. For example, 

around the time of childbirth, many women leave 

the workforce temporarily and, thus, may experience a large drop in their monthly income which 

would result in their becoming eligible for WIC. 

Annual income measures may obscure this fact 

and make it appear that these women had a consistent income above the income-eligibility thresholds. It is also impossible to identify women who 

are pregnant, post-partum, or breastfeeding in the 

CPS. 

Adjustments can be made to the CPS to account for many of these shortcomings. For example, an adjustment can be made to the annual income data in the CPS to account for monthly income fluctuations. Additionally, CPS estimates can 

use data on enrollment in TANF, Food Stamp, and 

Medicaid programs to account for adjunctive eligibility. 

SIPP Estimation

A second strategy for estimating eligibility is to 

use data from the SIPP, which can provide some 

advantages over the CPS. SIPP collects monthly 

income data so it can more accurately determine 

eligibility in a given month. This also allows the 

observation of income and eligibility over the 

course of a woman’s pregnancy, a time period that 

can be identified because infants are identified 

during their birth month. SIPP also contains information on enrollment in TANF, Food Stamps, and 

Medicaid so it can account for adjunctive eligibility. 

Despite these advantages, the SIPP methodology also has some disadvantages. For instance, 

like the CPS, it does not contain information on 

breastfeeding status. Additionally, mothers appear 

to be under-represented in the SIPP data compared to infants, leading to a potential underestimation of post-partum women. Because the SIPP 

data is very complex, the public release of the data 

lags behind the CPS. The data is not as timely, 

which is an important consideration in estimating 

WIC eligibility. 

Estimating Eligibles 

In the fall of 2004, the Food and Nutrition Service commissioned the Urban Institute to implement 

the methodology recommended by the Committee 

on National Statistics of the National Research 

Council. The estimates of WIC eligibles in this report were produced by the Urban Institute. 

How Many Women, Infants, and 

Children Are Eligible for WIC?

In 2003, the CPS calculation estimates that 

there are close to 13.5 million people eligible for 

WIC (Table 1). More than half of those (63.1% or 

about 8.5 million) eligible are children aged 1 to 4. 

The next largest category of people eligible for WIC 

is infants (17.5% or about 2.4 million). Pregnant 

women make up 1.2 million of the population eligible for WIC. Altogether, 1.4 million post-partum 

(breastfeeding and non-breastfeeding) women 

make up the balance of people eligible for WIC. 

Of the 13.5 million people estimated eligible for 

WIC in 2003, 71% had annual incomes below 

185% of poverty. The rest were eligible due to enrollment in TANF, Food Stamps, or Medicaid, 

and/or because they had periods of WIC income 

eligibility within the year. Women and infants were 

most likely to have been eligible due to periods of 

low income within the year. 

Number 

Eligible 

Number 

Participating 

Coverage 

Rate 

 

Pregnant Women 1,214,682 845,071 69.6% 

Breastfeeding 

Women 671,869 457,592 68.1% 

Post-partum Women 725,703 571,941 78.8% 

Infants 2,357,452 1,959,486 83.1% 

Children 8,498,839 3,850,275 45.3% 

Total WIC Eligibles 13,468,545 7,684,365 57.1% 

Table 1: Number Eligible, Participation, and Coverage Rate 

by Participation Category in 2003 

 
Office of Analysis, Nutrition, and Evaluation Page 3 

Comparing the CPS calculation to the SIPP 

calculation for the most recent year the SIPP is 

available (2002) shows that the SIPP calculation 

produces slightly higher eligible estimates for infants 

and children, but slightly lower numbers of pregnant 

women (see Figure 1). Overall, the numbers are 

similar and do not result in large biases in either 

direction. Because the results are so similar and the 

CPS data provides more timely estimates, the report 

focuses on the results generated by the CPS methodology. 

How Has the Number of Eligible Women, 

Infants, and Children Changed Over Time? 

The number of women, infants, and children 

eligible for WIC has remained fairly steady over time 

(see Figure 2). Between 1994 and 2003, the total 

number of persons eligible for WIC has ranged from 

a low of 12.0 million in 1999 to a high of 13.7 million 

people in 1994. As noted above, about 13.5 million 

people were eligible for WIC in 2003 (the most recent year for which data is available). When this 

trend is examined for each of the eligibility categories, we see that the trends over time are also fairly 

steady. 

What Proportion of the Population Eligible 

for WIC Receives WIC?

The proportion of the population eligible for WIC 

that actually participates in WIC has changed over 

time (see Figure 3). In 1994, 47% of those eligible 

for WIC actually participated. This proportion increased throughout the late 1990’s, reaching a high 

of nearly 61% in 1999. This corresponds with both 

a decrease in the number of persons eligible and 

an increase in participation during this time when 

increased funding was available to the program. 

Since 2000 the proportion of the population eligible 

that participates has held steady at about 57%. 

Within participation categories, the proportion of 

the population eligible that participates varies. The 

lowest participation rates for eligible persons are for 

children—with coverage rates ranging from 35.5% 

in 1994 to 49.2% in 1999; 45% of those eligible 

participated in 2003. Infants consistently have the 

highest coverage rates. The proportion of the eligible population that participates in WIC ranges 

from a low of 74.5% in 1995 to a high of 86.6% in 

1998. Close to 83% of infants eligible for WIC participated in 2003. 

The coverage rates for women can vary, depending on which certification category is being 

examined. The proportion of pregnant women who 

are eligible for and participate in WIC has ranged 

from 64% in 2001 to 77.6% in 1998; about 69% of 

those eligible participated in 2003. A smaller proportion of eligible breastfeeding women participate 

in WIC compared to postpartum women who do not 

breastfeed; however, the proportion of eligible 

breastfeeding women who participate has increased over time, reaching a high of 67.4% in 

2003. The proportion of postpartum women has 

ranged from a low of 56.7% in 1994 to a high of 

81.9% in 1998; nearly 78% of those eligible participated in 2003. 

Figure 1: Eligibility Estimates for 2002 Compared to 

Participation

0

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Pregnant Women Infants Children

Participation Category

Number

CPS SIPP Participation

Figure 2: Number Eligible for WIC, 1994 through 

2003, Based on CPS

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2,000,000

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1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Year

Number Eligible

Infants Children Pregnant Women Breastfeeding Women Post-partum Women

Trends in WIC Funding 

Although WIC is a discretionary program, it is important to note that the 

funding has been sufficient to provide 

benefits to eligible persons seeking 

services. There have not been waiting 

lists to participate in WIC in recent 

years. 
Office of Analysis, Nutrition, and Evaluation Page 4 

Conclusions 

The new methodology provides more accurate 

estimates of the number of people eligible for WIC. 

The more accurate numbers help establish appropriate funding levels and assist program operations 

and outreach activities. 

Over time, the trends in the eligible population 

have fluctuated slightly as have trends in participation. However, the percentage of the eligible population who participates in WIC has never been 

above 90% for any certification category. Children 

have consistently had the lowest coverage of any 

group; estimates of childrens’ coverage have never 

exceeded 50%. For all groups eligible for WIC combined, the coverage rate in 2003 was 57.1%. This 

is consistent with WIC coverage levels for the past 

decade. 

References 

National Research Council. (2001). Estimating 

Eligibility and Participation for the WIC Program: 

Phase I Report. Committee on National Statistics, Division of Behavioral and Social Sciences 

and Education. Washington, DC: The National 

Academies Press. 

National Research Council. (2003). Estimating 

Eligibility and Participation for the WIC Program: 

Final Report. Committee on National Statistics, 

Division of Behavioral and Social Sciences and 

Education. Washington, DC: The National Academies Press.

USDA, Food and Nutrition Service. (1999). Estimating the Number of People Eligible for WIC and 

the Full-Funding Participation Rate: A Review of 

the Issues. 

Acknowledgements 

This report was prepared by Amanda Nothaft, Food 

and Nutrition Service, Office of Analysis, Nutrition, 

and Evaluation, based on tabulations prepared by 

Sandi Nelson, Urban Institute. Laura Castro, Jay 

Hirschman, and Alberta Frost commented on earlier 

drafts. 

Research about WIC is available online at: 

http://www.fns.usda.gov/oane/MENU/Published/

WIC/WIC.HTM 

Non-Discrimination Statement 

The U.S. Department of Agriculture (USDA) prohibits discrimination 

in all its programs and activities on the basis of race, color, national 

origin, age, disability, and where applicable, sex, marital status, 

familial status, parental status, religion, sexual orientation, genetic 

information, political beliefs, reprisal, or because all or part of an 

individual’s income is derived from any public assistance program. 

(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 to USDA, Director, Office of Civil 

Rights, 1400 Independence Avenue, SW, Washington, DC 20250-

9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). 

USDA is an equal opportunity provider and employer.

Figure 3: Percent of Population Eligible for WIC Receiving WIC 1994 to 2003, Based on CPS

0.0%

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1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Year

Percentage Receiving WIC

Infants Children Pregnant Women Breastfeeding Women Post-partum Women