United States

Department

of Agriculture

Economic

Research

Service

Electronic

Report

Food

Assistance

and Nutrition

Research

Report No. 44

February 2005

Children’s Consumption 

of WIC-Approved Foods

Victor Oliveira

Ram Chandran
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Children’s Consumption of WIC-Approved Foods/FANRR-44

United States

Department

of Agriculture

www.ers.usda.gov

An Electronic Report from the Economic Research Service

February 2005 

Food

Assistance

and Nutrition

Research

Report No. 44

Children’s Consumption of

WIC-Approved Foods

Victor Oliveira and Ram Chandran

Abstract

The WIC program offers supplemental foods to low-income women, infants, and

children. This study compared consumption patterns of WIC children with those

of three different comparison groups: eligible nonparticipating children living in

non-WIC households, eligible nonparticipating children living in WIC households, and children living in households whose income is too high to be eligible

for WIC. The study provides strong evidence that participation in the WIC program increases consumption of at least some types of WIC-approved foods.

Although WIC-participating children consumed significantly more calories from

WIC-approved foods than children in the two comparison groups of eligible nonparticipants, there was no significant difference in total calories consumed. The

results suggest that WIC foods replace non-WIC foods in the diets of children

participating in WIC rather than adding to their food consumption. This is the

first study to examine in detail children’s consumption of WIC-approved foods

by WIC status. Understanding WIC’s effect on the consumption of foods contained in the WIC food packages can help inform decisions on possible changes

to the packages. 

Keywords: WIC, Special Supplemental Nutrition Program for Women, Infants,

and Children, food packages, WIC-approved foods, Tobit regression analysis,

food consumption patterns, child nutrition.
Contents

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .iii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Overview of the WIC Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Participant Eligibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Participant Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Previous Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

The Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Classifying Children by WIC Status . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Determining WIC-Approved Foods . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Descriptive Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Regression Analysis of the Effects of WIC Participation . . . . . . . . . . .15

Regression Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Effects Associated With WIC Participation . . . . . . . . . . . . . . . . . . . . . .23

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

Appendix—History of the WIC Food Packages . . . . . . . . . . . . . . . . . . .34

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Summary

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) provides supplemental foods that are good sources of nutrients

typically lacking in the diets of the target population, as well as offering

nutrition education and health care referrals. The provision of supplemental

foods is assumed to lead to their increased consumption, which in turn is

expected to improve the health of program participants. However, the relationship between participation in WIC and increased consumption of WIC

foods has not been fully examined. Understanding WIC’s effect on the

consumption of foods in the WIC packages will help inform decisions on

possible changes to the packages. This report examines children’s consumption of these foods, using data from the Continuing Survey of Food Intake

by Individuals (CSFII) 1994-96, 1998—a time period that captures the

dramatic increase in the number of children participating in WIC during the

late 1980s and 1990s. 

On average, calories from WIC-approved foods account for at least onequarter of the total calories from food and beverages consumed by children.

To determine the effect of WIC participation on the consumption of WICapproved foods, the authors compared the consumption patterns of WIC

participants to those of eligible nonparticipants living in non-WIC households. Two additional comparison groups were constructed to account for

(1) the possibility of spillover effects, whereby WIC foods are shared

among non-WIC household members (eligible nonparticipants living in

WIC households), and (2) the effect of higher household incomes (ineligible

nonparticipants). 

After controlling for other observed factors, the authors found that WIC

participants consumed 24 to 45 percent more WIC-approved juice (about

68-128 grams), and 17 to 26 percent less of other beverages such as soft

drinks (about 70-108 grams), over the 2 days than those in each of the three

comparison groups. WIC participants also consumed about 75 percent more

WIC-approved cereal (about 18 grams) over the 2 days than those in two of

the three comparison groups. The findings support results from previous

studies in which WIC participation was associated with significantly lower

intake of added sugars. However, the analysis found little or no association

between participation in WIC and the consumption of other WIC-approved

foods. The fact that similar results were found among the different comparison groups provides stronger, more credible results than if one comparison

group were used. 

Results from the analysis show that WIC participants consumed significantly more calories (12-14 percent) from WIC-approved foods than each of

the three groups of nonparticipants. On the other hand, the participants

consumed significantly fewer calories from non-WIC foods than the two

groups of eligible nonparticipants. In terms of total calories consumed from

all foods and beverages, there was no significant difference between WIC

participants and the two groups of eligible nonparticipants. Thus, there is

little evidence that participation in WIC contributes to increased caloric

intake among those children eligible to participate. However, WIC participants consumed more total calories than children not eligible to participate

because their household income was too high. 

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Children’s Consumption of WIC-Approved Foods/FANRR-44
Numerous differences in the consumption of WIC-approved foods were also

found by race/ethnicity and geographic regions, suggesting strong cultural

and regional dietary patterns. Children’s consumption of WIC foods varied

by day of the week: the consumption of many WIC-approved foods

decreased on weekends. 

The study highlights the importance of determining which foods to include

in WIC food packages to influence change in the dietary patterns of participants in the program. 

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Economic Research Service/USDA

National Agricultural Library Cataloging Record:

Oliveira, Victor 

Children's consumption of WIC-approved foods. 

(Food Assistance and Nutrition Research report ; no. 44)

1. Special Supplemental Nutrition Program for Women, Infants, 

and Children (U.S.)

2. Children—United States—Nutrition. 

2. Food consumption—United States.

I. Chandran, Ram. 

II. United States. Dept. of Agriculture. Economic Research Service.

III. Title.

HV696.F6

The U.S. Department of Agriculture (USDA) prohibits discrimination in 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 Ave., SW, Washington, DC 20250-

9410, or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity

provider and employer.

Cover photos:

Girl drinking milk: Courtesy of National Dairy Council/Dairy Management Inc.

Other photos: USDA
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Introduction

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) provides a package of supplemental foods, nutrition education,

and referrals to health care to low-income women, infants, and children up

to age 5 who are at medical or nutritional risk. The cornerstone of the WIC

program is its supplemental food packages that provide foods “containing

nutrients determined to be beneficial” for the target population (7 CFR

246.2).1 WIC can also affect the diet quality of recipients through its nutrition education program, designed to help recipients achieve a positive

change in their food habits through the optimal use of the supplemental

foods and other nutritious foods. WIC is based on the premise that early

food interventions during times of critical growth and development will not

only improve the health status of participants, but will help prevent later

health problems. 

WIC regulations specify the types of foods that can be included in the WIC

food packages, which are rich in one or more of the five target nutrients—

protein, iron, calcium, and vitamins A and C. Although the types of food in

the packages have remained basically unchanged since the 1970s, food

consumption patterns have changed, nutritional standards have been revised

based on current scientific knowledge, the prevalence of obesity and overweight has increased markedly, and the WIC participant population has

become more ethnically diverse (see the appendix for a detailed discussion

of the history of the WIC food packages). As a result, the composition of

the WIC food packages has received increased attention, and some authorities have recommended changes to better help program participants meet

nutritional standards for a healthy diet. For example, in 2000 the National

Association of WIC Directors recommended a number of changes to the

WIC food packages, such as including fruits and vegetables for all women

and children, reducing the maximum quantity of milk for children, and

offering foods that reflect the cultural dietary patterns of participants

(National Association of WIC Directors, 2000). Congress in 2001 stated

that encouraging WIC children to eat fresh fruits and vegetables is crucial to

establishing healthful, nutritious eating habits for life, and it urged USDA’s

Food and Nutrition Service (FNS) to look into ways to increase the

consumption of produce by WIC participants (U.S. House of Representatives, 2001). In 2002, the American Dietetic Association recommended

flexibility in the WIC food packages in order to address cultural food practices and choices and participants’ nutrition needs, consistent with national

guidelines (American Dietetic Association, 2002). 

USDA recently solicited public comments on redesigning the WIC food

packages to determine if they should be revised to better improve the nutritional intake, health, and development of participants, and if so, what

specific changes should be made (68 FR 53903).2 Understanding WIC’s

effect on the consumption of the types of foods in the packages will help

inform decisions on possible changes.

This report examines the consumption of the types of food provided in the

WIC food packages, focusing on children 1-4 years of age, who make up

half of all WIC participants.3 The two major issues to be addressed are: 

1The supplemental food package

was consistently ranked by pregnant

and postpartum women as being the

leading positive attribute of the program in a recent WIC study (Fox et

al., 1998). Food costs accounted for

$3.2 billion, or about 71 percent of the

total cost of the program in fiscal 2003

(USDA, FNS, December 2003).

2USDA has contracted with the

Institute of Medicine of the National

Academies to develop cost-neutral recommendations to modify the WIC food

packages based on the best available

scientific information. A preliminary

report was released in August 2004 and

the final report is expected to be

released in February 2005 (Institute of

Medicine, 2004).

3Because of their limited diet,

infants less than 1 year old were

excluded from this analysis. Women

were excluded due to the small number

of women in the dataset used in this

study who were identified as WIC participants.
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How does participation in WIC affect the consumption of WIC-approved

foods? Consumption of the food in the WIC packages is expected to

improve the diet and nutritional status, and thus the health, of program

participants. One of the key assumptions is that providing the supplemental

foods leads to their increased consumption. However, the relationship

between participation in WIC and the consumption of WIC foods has not

been fully examined. 

Does participation in WIC result in increased caloric intake? The dramatic

increase in the prevalence of overweight and obesity among children is one

of the most serious public health concerns in the United States today

(National Center for Health Statistics, 2003). Questions have been raised as

to whether providing free supplemental foods through WIC increases the

caloric intake of recipients. 

The source of data for this study is the Continuing Survey of Food Intakes

by Individuals (CSFII) 1994-96, 1998, a national survey designed to

measure what Americans eat and drink. The study period captures the tail

end of the dramatic increase in the number of children in WIC during the

late 1980s and 1990s, when the number more than doubled (fig. 1).4 Nearly

one-quarter of the Nation’s children from 1 to 4 years of age now participate

in WIC. 

Figure 1

Average monthly number of children participating in WIC, 

FY 1974-2003

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Millions

1974 76 78 80 82 84 86 88 90 92 94 96 98 2000 02 

Fiscal year

4WIC is not an entitlement program. Rather, it is a discretionary

grant program funded by appropriations law on an annual basis.

Therefore, the number of participants

that can be served each year depends

upon the annual appropriation and the

cost of operating the program. The

program provides services to as many

eligible people as funding allows.

Because WIC may not be able to serve

all eligible applicants in all years, it

has a priority system to ensure that

those people at the greatest nutritional

risk receive program benefits. The

expansion of the WIC program during

the late 1980s and 1990s, as a result of

increased congressional funding as

well as State cost-containment measures, allowed a greater number of

lower priority children to participate in

the program. As a result, the role of

the priority system in allocating available program slots among applicants

decreased in importance relative to

previous years when program funds

were more limited. The decrease in

the number of WIC participants from

1997 to 2000 was predominantly

among children, which may reflect

favorable economic conditions that

decreased the demand for food assistance (mothers of older children may

be better able then pregnant women

and women with infants to take advantage of increased job opportunities and

higher wages resulting from economic

growth). 
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Overview of the WIC Program

WIC supplies a package of benefits to a targeted group of participants who

must meet a number of eligibility requirements. 

Participant Eligibility

To qualify for WIC, applicants must meet categorical, residential, income,

and nutritional risk eligibility requirements.

(1) Categorical eligibility. To participate in the WIC program, a person

must be:

• A pregnant woman (includes up to 6 weeks postpartum),

• 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 fifth birthday.

(2) Residential eligibility. WIC applicants must live in the State where they

establish eligibility and receive benefits.

(3) Income eligibility. The family income of WIC applicants must meet

specified guidelines. All WIC State agencies currently set the income

cutoff at 185 percent of the Federal poverty guidelines. Applicants who

participate in the Food Stamp, Medicaid, or Temporary Assistance for

Needy Families (TANF) programs, or who have certain family members

who participate in the Medicaid or TANF programs, are adjunctively

income eligible, that is, they are deemed to meet the income eligibility

criterion automatically.

(4) Nutritional risk. Applicants must be at nutritional risk, as determined by

a health professional such as a physician, nutritionist, or nurse. Federal

regulations recognize five major types of nutritional risk for WIC eligibility: (1) detrimental or abnormal nutritional conditions detectable by

biochemical or anthropometric measurements ; (2) other documented

nutrition-related medical conditions; (3) dietary deficiencies that impair

or endanger health; (4) conditions that directly affect the nutritional

health of a person, including alcoholism or drug abuse; and (5) conditions that predispose persons to inadequate nutritional patterns, or nutritionally related medical conditions, including, but not limited to, homelessness and migrancy (7 CFR 246.2). 

WIC children are generally eligible to receive benefits for 6-month periods,

after which they must be recertified to continue to participate. 

Participant Benefits

The WIC program offers three types of benefits to participants: a supplemental food package, nutrition education, and referrals to health and other

services. 

(1) Supplemental food package. WIC provides participants with supplemental foods that are high in five target nutrients: protein, calcium, iron, and
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vitamins A and C. There are seven food packages, designed for different

target populations: (1) infants through 3 months, (2) infants 4-12

months, (3) children 1-4 years old, (4) pregnant and breastfeeding

women (basic), (5) nonbreastfeeding postpartum women, (6) exclusively

breastfeeding women (enhanced), and (7) children or women with special dietary needs. The WIC-authorized foods in the package for children 1-4 years old are iron-fortified adult cereal, vitamin C-rich fruit

and/or vegetable juice, protein/iron-rich eggs, calcium/protein-rich milk

and cheese, and protein-rich peanut butter and dried beans/peas, as

shown in table 1. The average cost of the WIC food package for children in fiscal 1998, the last year of the study period, was $34.33 per

month (USDA, FNS, November 2000). 

WIC regulations specify the maximum quantities of supplemental foods

that may be prescribed to participants (7 CFR 246.10). The authorized

maximum monthly allowances of all WIC foods must be made available

to participants if medically and nutritionally warranted.5 Local WIC

agencies may tailor individual food packages based on participants’

nutritional or health status, their nutritional risk factors, and their food

restrictions, intolerances, and preferences. For maximum effect on nutritional status, the WIC food package is intended to be consumed solely

by the individual participant and not by other family members (57 FR

56233).

Typically, food benefits are provided to participants in the form of a

food “instrument”—a voucher or food check—that they use to purchase

approved foods at authorized grocery stores.6 The food instrument specifies the types and amounts of supplemental foods that can be obtained. 

(2) Nutrition Education. WIC makes nutrition education, including breastfeeding promotion and support, available to all participants (or to the

parents or caretakers of infant or child participants). The nutrition education is designed to achieve two broad goals: (1) to stress the relationship between proper nutrition and good health and to raise awareness

about the dangers of using drugs and other harmful substances during

pregnancy and while breastfeeding, and (2) to assist the nutritionally atrisk individual in achieving a positive change in food habits—resulting

in improved nutritional status and the prevention of nutrition-related

problems—through the use of the supplemental foods and other nutritious foods (7 CFR 246.11). Local WIC agencies are required to offer

participants at least two nutrition education sessions during each 6-

month period, in either an individual or group setting. However, individuals who do not attend the nutrition education activities are not

denied the WIC food package.

(3) Referrals to Health Care and Social Services. WIC was designed to

operate as an adjunct to health care. Local WIC agencies assist WIC

participants in obtaining health care and social services (such as food

stamps, Medicaid, and immunizations), either through onsite health services or referrals to other agencies. 

5Recipients are not required to

accept all WIC foods offered to them.

6The exceptions are Vermont, in

which the WIC foods are delivered to

the participant’s home, and

Mississippi and parts of Chicago,

where participants pick up the WIC

foods from facilities operated by the

State or local agency.
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Table 1—WIC food package for children 1 to 5 years: maximum monthly quantities1

Milk:

Fluid whole milk.................... 24 qts (22.7 L)

or

Fluid skim or low fat milk..........May be substituted for fluid whole milk on a quart-for-quart (.9 L) basis.

or

Cultured buttermilk................. May be substituted for fluid whole milk on a quart-for-quart (.9 L) basis.

or

Evaporated whole milk............May be substituted for fluid whole milk at the rate of 13 fluid oz (.4 L) 

per qt (.9 L) of fluid whole milk.

or

Dry whole milk....................... May be substituted for fluid whole milk at the rate of 1 lb (.4 kg) per 3 qts

(2.8 L) of fluid whole milk.

or 

Nonfat or lowfat dry milk.......... May be substituted for fluid whole milk at the rate of 1 lb (.4 kg) 

per 5 qts (4.7 L) of fluid whole milk.

or 

Cheese................................May be substituted for fluid whole milk at the rate of 1 lb (.4 kg) per 3

qts (2.8 L) of fluid whole milk. The maximum amount that may be substituted is 4 lbs (1.8 kg).2

Eggs:

Fresh eggs...........................2 doz. or 2 1⁄2 doz.

or 

Dried egg mix........................May be substituted at the rate of 1.5 lb (.7 kg) egg mix per 2 doz. fresh

eggs or 2 lb (.9 kg) egg mix per 2 1⁄2 doz. fresh eggs.

Cereals (hot or cold)................. 36 oz dry (1 kg)

Juice:3

Single-strength juice.............. 276 fluid oz (8.2 L)

or

Frozen concentrated juice........288 fluid oz reconstituted (8.5 L)

Legumes:

Dry beans or peas.............. 1 lb (.4 kg)

or

Peanut butter........................ 18 oz (.5 kg)

1As defined in the Code of Federal Regulations (7 CFR 246.10). 2Additional cheese may be issued on an individual basis in cases of lactose intolerance, provided the need is documented in the participant’s

file by the competent professional authority. 3Combinations of single-strength and frozen concentrated juice may be issued as long as the total volume does not exceed the amount specified for single-strength juice.
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Previous Studies

Recent research on the effect of WIC on children’s food consumption is

limited to two studies that estimated the consumption of WIC foods without

controlling for other factors.7 Because reported differences in consumption

levels between WIC participants and nonparticipants may actually be due to

factors such as age or income, and not to whether they participated in WIC,

not controlling for these other factors can confound the measurement of

effects due to WIC. Therefore, the reported differences in consumption

between WIC participants and nonparticipants in these two studies should

be viewed as descriptive and not necessarily as a result of WIC. 

The first study was based on a survey of 2-year-old children in 1994-97 that

compared the usual eating habits of WIC children with other low-income

children (Burstein et al., 2000). The study used a nonrepresentative sample

of children in 10 sites from families with incomes less than 100 percent of

poverty. Families were asked whether their child usually consumed three

types of WIC foods: milk, cheese, and juice. The study found that WIC

children were significantly more likely than other low-income children to

consume each of the three types of WIC foods at least once a day. 

A more recent descriptive study of children ages 12-24 months compared

WIC participants with all nonparticipants, regardless of nonparticipants’

income (Ponza et al., 2004).8 WIC participants were more likely than

nonparticipants to consume 100-percent juice and cow’s milk, as well as

sweetened beverages and fruit-flavored drinks. Similar proportions of WIC

participants and nonparticipants consumed presweetened and non-presweetened cereals, eggs, peanut butter (including nuts and seeds), and cheese.

Although the mean intakes of food energy for both WIC participants and

nonparticipants exceeded estimated energy requirements (EER), the difference between mean energy intake and the EER was greater for WIC participants than nonparticipants.

Although recent information about WIC’s impact on children’s consumption

of WIC foods is limited to two descriptive studies, a number of nationallevel studies used analytical procedures to control for other factors and

found positive associations between WIC participation and nutrient or

dietary intake among WIC-age children. Although the present report

focuses on food consumption, a brief review of the nutrient or dietary

analysis of WIC provides helpful background. 

Using data on children in households with income less than 130 percent of

poverty from the 1989-91 CSFII, Rose et al. (1998) found that participation

in the WIC program was associated with a significant increase in the intake

of a number of nutrients, including iron and protein. In a study based on

data from the 1994-96 CSFII of children who were income-eligible for WIC

(proxied by annual household income less than 200 percent of poverty),

Oliveira and Gundersen (2000) found that participation in WIC was associated with significantly increased intake of several WIC-targeted nutrients—

iron, vitamin C, and vitamin A. After limiting the analysis to children living

in a household with an infant or woman on WIC, the authors found that

participation in WIC had a positive and significant effect on the intake of

iron, folate, and vitamin B-6. 

7This review focused on recent

studies because results from studies

based on data collected before the dramatic expansion of the child component of WIC may not be applicable to

the current situation, in which WIC

benefits are more widely available to

children.

8In other words, the group of nonparticipants included both children eligible to participate in WIC and children who were ineligible. 
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Chandran (2003) used the 1994-96, 1998 CSFII data set to examine the

effect of WIC participation on food consumption and diet quality of children 2-4 years of age. Diet quality was assessed using USDA’s Healthy

Eating Index (HEI), which incorporates 10 components of dietary guidelines. The study found that participation in WIC was associated with

improved diet quality as measured by HEI and several of its components.

The analysis also found that WIC participation was associated with reduced

consumption by children of added sugars (i.e., those that do not occur naturally in the foods themselves).

Another study using the 1994-96, 1998 CSFII dataset found that among

children in households with incomes less than 130 percent of poverty, WIC

had a beneficial effect on the intake of fat, carbohydrates, added sugar, and

fruit (Siega-Riz et al., 2004).9 Among children in households with incomes

from 130 percent to 185 percent of poverty, WIC had a beneficial effect on

the intake of added sugar and fruit. No statistically significant differences

were found in total energy intake by WIC status. 

Although these studies found that participation in WIC is associated with

improved diets or greater intake of WIC target nutrients, the outcomes may

not necessarily occur from the increased consumption of WIC foods. They

could occur, for example, if receipt of WIC benefits frees up food dollars

that are spent on foods not provided in WIC food packages but that are still

high in WIC target nutrients, or if the nutrition education provided through

WIC leads to improved diets with increased consumption of non-WIC foods

high in the target nutrients.10

The Data

The source of data for this study was the Continuing Survey of Food

Intakes by Individuals (CSFII) 1994-96, 1998 conducted by USDA’s Agricultural Research Service (USDA, ARS, 2000). The CSFII 1994-96

collected information from people of all ages. The Supplemental Children’s Survey (or CSFII 1998), which only collected data from children

less than 10 years of age, was designed so that the data could be combined

with those from the 1994-96 survey.11 Both surveys use a complex multistage area sample design to obtain nationally representative samples of

people in U.S. households.

The CSFII 1994-96, 1998 contains information on the socioeconomic characteristics of individuals as well as on their food intake, specifically, the

kinds and amounts of food consumed on each of 2 nonconsecutive days,

using 24-hour dietary recalls. Day 1 data on children were collected in

person with adult proxies—preferably the person responsible for preparing

the child’s meals—providing the food intake data for children. Most Day 2

data were also collected in person, although some of the interviews were

conducted by telephone. Both the Day 1 and Day 2 questionnaires used a

multiple-pass method to maximize the respondent’s ability to remember

what was consumed. Measuring guides were used to help the respondent

estimate the amounts eaten. Descriptions of every food item consumed

were obtained from the respondents and then matched to descriptions of

foods in a food coding database. 

10Self-selection bias is another potential factor in explaining previous

results that found that WIC participation is associated with increased nutrient intake. People who participate in

WIC may be more concerned about

nutrition and more motivated to

improve their own or their child’s

nutritional status than eligible persons

who choose not to participate in the

WIC program. 

9That is, WIC participation was

associated with increased intake of

carbohydrates and fruit and decreased

intake of fat and added sugars. 

11The Supplemental Children’s

Survey was conducted in response to

the Food Quality Protection Act of

1996, which required USDA to provide data from a larger sample of children for use by the Environmental

Protection Agency in estimating exposure to pesticide residues in children’s

diets.
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The CSFII 1994-96, 1998 contained information on 6,748 children, of

whom 118 were being breastfed or did not have their WIC status listed and

were thereby excluded from the analysis. An additional 1,111 children who

did not have 2 days of consumption data were also excluded from the

analysis, resulting in a sample of 5,519 children.12 

Classifying Children by WIC Status

To be eligible for WIC, family income must fall at or below 185 percent of

the Federal poverty guidelines or the child must participate in the Food

Stamp, Medicaid, or Temporary Assistance for Needy Families (TANF)

programs (or have certain family members who participate in the Medicaid

or TANF programs), and the child must also be individually determined to

be at “nutritional risk” by a health professional. Because the CSFII data do

not allow for the determination of nutritional risk, WIC eligibility for this

study was proxied solely by income, as determined by the annual income of

the household.13 Past research suggests that WIC income eligibility estimates based on annual income may underestimate income eligibility for

WIC as determined by local WIC agencies (Gordon et al., 1997).14 In order

to include all children who were likely to have met the WIC income-eligibility criteria at some point during the year, this report considered children

in households with annual income at or below 200 percent of the poverty

guidelines to be income-eligible for WIC. Children who were authorized to

receive food stamps, or who lived in a household that received income from

the Aid to Families with Dependent Children (AFDC) or TANF programs,

were considered to be WIC-eligible regardless of income.15 Although

participation in Medicaid also makes a child income-eligible for WIC, the

CSFII did not collect information on Medicaid participation. Children

living in a household in which someone was participating in WIC were

considered to be eligible for WIC regardless of income. 

The 5,519 children included in the sample were assigned to one of four

mutually exclusive groups determined by WIC status (table 2). These four

groups included WIC participants (children who were participating in the

WIC program at the time of survey) and two groups of eligible nonparticipants: children who resided in a household in which no one was participating in WIC and children who, while not participating in WIC, lived in a

household in which some other member of the household was a participant.

Children in WIC households were separated from other eligible nonparticipating children in order to control for possible spillover effects that could

bias the results of the study. Spillover effects may occur if a person’s

participation in WIC affects the consumption patterns of other people in the

household. For example, this could happen if: (1) receipt of WIC benefits

frees up food dollars that are spent on WIC-type foods for nonparticipating

children; (2) the nutrition education received by WIC women (the primary

meal preparers in most households) results in increased consumption of

certain WIC-type foods by other household members; or (3) WIC foods are

shared among non-WIC household members. Although the WIC food

package is intended to be consumed solely by the individual participant and

not by other family members, sharing of WIC foods may occur.16

12Of the 1,111 children with less

than 2 days of data, 862 had no days

of data and 249 had only 1 day of

data.

13The inability to use the CSFII to

determine whether an individual meets

the nutritional risk criteria has no practical effect in determining WIC eligibility status for this study. WIC applicants are required to meet only one of

a number of nutritional risk criteria to

be eligible for WIC. Research has

determined that “nearly all U.S.

women and children” meet the criteria

based on failure to meet Dietary

Guidelines and thus are at nutritional

risk (Institute of Medicine, 2002).

14WIC regulations state that local

WIC agencies, in determining the

income eligibility of an applicant, may

consider either the income of the family during the past 12 months or their

current income to determine which one

more accurately reflects the family’s

status (7CFR 246.7). More individuals

may be eligible if the determination is

based on monthly or biweekly rather

than annual income (for example, during a period of unemployment).

15The Personal Responsibility and

Work Opportunity Reconciliation Act

of 1996 replaced the AFDC program

with the TANF program. 

16The degree to which the sharing

of WIC foods occurs is not known. 
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The fourth group of children included in the analysis were ineligible

nonparticipants (children not eligible for WIC as determined by high household income and nonparticipation in the Food Stamp and AFDC/TANF

programs). There are fundamental differences in household resources,

education levels, and nutrition knowledge between adults caring for children

eligible for WIC and adults caring for children whose family income is too

high to be eligible.17 The differences may affect food consumption patterns.

Therefore, the most relevant comparison of the effects of WIC will be

between WIC participants and other low-income children. However, for

completeness, the group of children ineligible to participate in WIC was

also included in this analysis. The finding of consistent results in comparisons between WIC children and all three groups of nonparticipants,

including those ineligible to participate, would suggest stronger, more credible results.18

Determining WIC-Approved Foods

The CSFII food coding database consists of almost 7,500 unique food

codes, each including a description of the food. The determination of which

codes represent “WIC-approved” foods was inexact. Federal WIC regulations specify the types of supplemental foods that may be prescribed to WIC

participants (7 CFR 246.10). However, each State WIC agency is responsible for identifying the specific foods authorized for use in that State from

among those authorized by the Federal regulations.19 For example, States

can determine the physical form of the WIC food (for example, evaporated

or fresh fluid milk), specific food brands, food packaging (cans, cartons, or

bottles), flavors or varieties (e.g., orange or cranberry juice), and food

container sizes. As a result, the specific types of foods included in WIC

food packages vary across States.20 The CSFII does not identify the State

of residence of the survey respondent, nor does the description of the foods

in the CSFII food coding database always provide enough information to

determine whether that food exactly matched the types of foods approved

for WIC.21 ERS researchers identified the food codes that seemed to best

Table 2—Number of children 1-4 years of age in the sample by WIC status

Number of 

children WIC status

1,108 WIC participant—children participating in WIC at time of interview

1,602 Eligible nonparticipant (non-WIC household)—nonparticipating child who is eligible for WIC based

on income and resides in a non-WIC household

208 Eligible nonparticipant (WIC household)—nonparticipating child who is eligible for WIC based

on income and resides in a WIC household

2,601 Ineligible nonparticipant—nonparticipating child who is ineligible for WIC based on income 

5,519 Total children included in the analysis

Note: Of the 6,748 children in the CSFII 1994-96,1998 dataset, 1,229 were either breastfeeding or had less than 2 days of dietary intake

data, or their WIC status could not be ascertained and they swere subsequently dropped from the analysis.

17At least some of these differences

between WIC participants and ineligible children are unobservable and can

not be controlled for by statistical procedures. 

18For example, if WIC children

were found to consume significantly

more WIC foods than all three groups

of nonparticipants, there is more confidence that participation in WIC leads

to increased consumption of WIC

foods.

21For example, the food code did

not indicate whether the frozen concentrate fruit juice contained at least

30 milligrams of vitamin C per 100

milliliters of reconstituted juice as

required by Federal WIC regulations.

19Factors that influence State decisions on what foods to allow include

cost considerations, participant satisfaction, and ease of administration. In

addition, States can impose more stringent nutritional standards than those

specified in the Federal WIC regulations (Kirlin et al., 2003).

20For information on how the lists

of WIC-approved foods varies by

State, see Kirlin,et al., 2003
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represent “WIC-approved” foods, based on Federal WIC program regulations and a review of selected State lists of WIC-allowed foods (see table 3

for a description of the foods designated as WIC-approved foods for this

study). This report examines the consumption of the types of foods provided

through WIC, regardless of whether the food was actually purchased

through WIC.22 Therefore, all WIC-type foods, even those purchased

outside of WIC-authorized distribution systems (e.g., in a restaurant), are

considered to be “WIC-approved” for this report.

This study focuses on the types of food provided in the WIC food package

for children—cereal, juice, milk, cheese, eggs, peanut butter, and

beans/peas. WIC foods are distributed to participants by quantity (i.e., a

maximum of 36 ounces of dry cereal per month), and quantities vary across

WIC foods. A weight-based measure, grams, was used to determine the

amount of the individual WIC-approved food consumed. In general, WICapproved foods that were one of several food items in a food dish were

excluded from this analysis when the amount (in grams) of the WIC food

consumed was not specified in the dataset. This is not an issue for WICapproved foods, such as cereal and juice, that are rarely combined with

other foods.23 However, other WIC-approved foods, such as eggs or

cheese, are more often combined in dishes with other foods.24 This

problem is lessened somewhat by the fact that young children are probably

more likely than adults to consume single-item foods and less likely to

consume dishes comprised of combinations of foods.

Since this study is also interested in whether WIC is contributing to overweight, the food energy content, measured in calories, was collected for the

amount of WIC-foods consumed, the amount of non-WIC foods consumed,

and the total amount of food consumed. Milk drunk by young children is

often sweetened or flavored, which increases the calories consumed. Similarly, fat is often added to eggs and beans and peas during cooking,

increasing total calories. In measuring the calories consumed from all WICapproved foods, only the milk, eggs, and beans/peas were included for

which the CSFII listed the calories separately from those of other ingredients added after purchase.25

Descriptive Analysis

This section discusses the demographic and socioeconomic characteristics

of children and their consumption levels of selected foods by their WIC

status: WIC recipient, eligible nonparticipant in a non-WIC household,

eligible nonparticipant in a WIC household, or ineligible nonparticipant.

The estimates in the tables were computed using appropriate sample

weights. However, statistical testing was not conducted because the estimates reported here are for descriptive purposes and for suggesting possible

directions for the analytical procedures that follow. 

WIC recipients are generally younger than children in the other three

groups, reflecting the decline in children’s participation in WIC as they get

older (table 4). WIC recipients, as well as eligible nonparticipants in WIC

households, are more likely than the other two groups to receive food

stamps and to be Black or Hispanic. As expected, ineligible nonparticipants

22The CSFII does not collect information on which foods were obtained

through WIC. However, since one of

the objectives of the WIC program is

to improve food habits, it is important

to examine the overall consumption of

WIC-type foods, regardless of source.

23Although cereal is often eaten

with milk, the CSFII reports the

amounts of the cereal and milk consumed separately.

24Although milk consumed by

young children is often sweetened or

flavored after purchase, such milk,

even when the amount of the flavoring

or sweetener was not separated from

the milk in the dataset, was included as

WIC-approved milk since milk

accounts for the vast majority of the

beverage’s weight. Similarly, the milk

added to pudding mix was included as

WIC-approved milk.

25In other words, milk in which

chocolate syrup was added after purchase or milk added to pudding mix

were excluded from the total count of

calories from WIC-approved milk

when the added calories from the

chocolate syrup or pudding mix were

not reported separately in the dataset. 
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Table 3—“WIC-approved” foods and other food categories as defined in this study

WIC-approved milk (weight-based)

Includes: fluid cow’s milk (regardless of fat content), low-lactose milk, buttermilk, dry (powdered) milk, evaporated milk, 

acidophilus milk, goat’s milk, milk flavored after purchase, milk added to cocoa mix, and the milk added in making pudding 

at home.

Excludes: human milk, calcium-fortified milk, condensed milk, soy or rice milk, imitation milk, milk beverages, milk drinks such as

Yoo-Hoo, milk shakes, milk purchased already flavored, and milk that was one ingredient in a multi-ingredient dish other than

pudding (such as soup) when the amount of milk consumed was not specified.1

WIC-approved milk (calorie-based)

Same varieties as for WIC-approved milk (weight-based) except that it excludes milk with flavorings added after purchase and

milk added to puddings and cocoa, when the calories from the milk could not be separated from the calories from flavorings and

pudding mix.

WIC-approved juices

Includes: all 100-percent (no added sugar) citrus, noncitrus, vegetable, and tomato juice, regardless of form (canned, bottle, carton, fresh).

Excludes: sweetened juices, juice or fruit drinks, juice cocktails, and ciders.

WIC-approved cereals

Includes: most hot or ready-to-eat national brands of cereal approved for WIC.

Excludes: most private or store brand cereals.

2

Other cereals

All cereals except WIC-approved cereals.

WIC-approved cheese

Includes: the following natural or processed cheeses: cheddar, brick, american, colby, colby jack, monterey, mozzarella, muenster, provolone, and swiss, including lowfat and low-sodium versions.

Excludes: other kinds of cheese as well as cottage cheese, cheese spread, cream cheese, and imitation cheese. Cheese mixtures were also excluded, i.e., cheese that was one ingredient in a multi-ingredient dish (e.g., cheese soup or cheese sandwich),

when the type or amount of cheese consumed was not specified.

WIC-approved eggs (weight-based)

Includes: all eggs, regardless of cooking method (scrambled, fried, boiled, etc.) and dried-egg mix.

Excludes: eggs that that were one ingredient in a multi-ingredient dish (e.g., egg foo yung or omelet with cheese and ham),

when the amount of eggs consumed was not specified.

WIC-approved eggs (calorie-based)

Same as WIC-approved eggs (weight-based) defined above, except excluding eggs with fat added during cooking.

WIC-approved peanut butter

Includes: low or reduced sodium.

Excludes: reduced fat peanut butter, vitamin- and mineral-fortified peanut butter, and peanut butter with added ingredients

such as jelly.

WIC-approved beans or peas (weight-based)

Includes: dry beans (such as white, black, brown, bayo, fava, lima, pink, pinto, red kidney, and mung bean), dry peas (cowpeas,

chickpeas, and split peas), and lentils.

Excludes: bean, pea, or lentil mixtures, i.e., beans or peas that were one ingredient in a multi-ingredient dish (e.g., pea or bean

soup), when the amount of beans or peas consumed was not specified.

WIC-approved beans or peas (calorie-based)

Same as WIC-approved beans or peas (weight-based) defined above, except excluding dry beans, peas, and lentils with fat

added during cooking.

Other beverages

Includes: soft drinks, juice drinks, lemonade, coffee, and tea.

Excludes: milk and milk drinks, fruit juice, and fluid replacement drinks (e.g., Pedialyte).

1Although Federal WIC regulations do not specifically disallow flavored milk, examination of the WIC-allowable food lists from a sample of 14

States found that all of the States specifically excluded flavored milk. 2The CSFII dataset identified few store brands. Store brands were estimated to account for 10 percent of the WIC cereal market share in 1999

(Private Label Manufacturers Association, 2000).
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Table 4—

Socioeconomic and demo

graphic characteri

stic

s of children by WIC 

statu

s

Eligible Eligible 

nonparticipants nonparticipants Ineligible

All children WIC recipients non-WIC household WIC household nonparticipants

Child characteristics:

Age:

1 year 24.3% 32.3% 19.7% 23.6% 23.5%

2 years 25.0% 26.3% 24.5% 20.7% 25.1%

3 years 25.6% 21.8% 26.1% 25.2% 26.9%

4 years 25.1% 19.5% 29.7% 30.5% 24.5%

Mean age (years) 2.5 2.3 2.7 2.5 2.6

Sex:

Male 50.8% 50.9% 51.4% 49.3% 50.6%

Female 49.2% 49.1% 48.6% 50.8% 49.4%

Race/ethnicity:

White (non-Hispanic) 60.8% 38.3% 49.8% 27.7% 78.6%

Black (non-Hispanic) 16.9% 28.7% 22.7% 31.8% 7.7%

Hispanic 16.1% 26.7% 21.3% 33.7% 7.6%

Other (non-Hispanic) 6.2% 6.3% 6.2% 6.8% 6.2%

Food stamp recipient 18.5% 49.1% 25.5% 43.8% 0.0%

Household characteristics:

Homeowner 55.3% 28.9% 35.6% 31.6% 78.8%

Assets over $5,000 33.3% 5.9% 11.0% 6.2% 58.9%

Single-headed household 19.1% 36.3% 29.3% 36.0% 5.2%

Annual household income ($) 39,870 18,255 20,305 20,925 60,968

Income as percent of poverty 195.4 102.5 117.1 107.1 283.4Household size (persons) 4.4 4.8 4.6 5.5 4.1

Head's schooling (years) 12.8 11.1 11.7 11.8 14.3

Geographic characteristics:

Region:

Northeast 19.4% 17.7% 16.2% 10.6% 22.5%

Midwest 23.0% 23.2% 23.8% 10.2% 23.4%

South 33.1% 33.9% 33.3% 38.5% 32.3%

West 24.5% 25.2% 26.6% 40.6% 21.8%

Urbanization:

Central city 33.3% 43.6% 36.5% 47.6% 26.2%

Suburbs 48.3% 33.7% 41.5% 38.1% 58.8%

Rural 18.4% 22.7% 22.0% 14.4% 15.0%
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appear to be better off relative to the other three groups, as measured by

socioeconomic characteristics such as annual household income, home

ownership, assets, and head of household’s years of schooling. They are

also less likely to live in a single-headed household, in central cities, or in

rural areas.

Within the two groups of eligible nonparticipating children, those who

resided in a WIC household were less likely to be White and more likely to

be Black or Hispanic, to receive food stamps, live in larger households, and

reside in the West or in central cities. 

Table 5 shows the average consumption (measured in either grams or calories) of the foods (including beverages) in the WIC food package for children, over the 2 days in which intake data were collected.26 The

WIC-approved cereal, juice, milk, eggs, cheese, and peanut butter refer to

the specific types of these foods that are approved for the WIC program as

defined in table 3. WIC-approved milk, eggs, cheese, peanut butter, and dry

beans/peas account for practically all of these food items that are consumed

by children. However, WIC-approved cereals account for only one-third

(33.2 percent) of the total quantity of all cereals consumed by children and

WIC-approved juices compete with other non-WIC beverages (such as soft

drinks) in the diets of children.27 Thus, the amounts of other cereal and

other beverages (excluding milk) consumed by children are also presented

in table 5. In terms of grams of food consumed, the data in table 5 indicate

that WIC participants consumed more WIC-approved cereal, juice, and milk

than the other three groups of participants. On average, calories from WICapproved foods account for one-quarter (24.7 percent) of the total calories

from food and beverages consumed by children.28

Approximations of the maximum amounts (in grams) of the foods provided

in the WIC food packages over a 2-day period are shown in the last column

of table 5. A comparison of the average amount of WIC-approved foods

consumed by WIC participants with the prorated maximum 2-day amount of

foods provided by the WIC food package indicates that WIC participants

are consuming far less than the maximum amounts provided by WIC. For

example, WIC children consumed an average 32.9 grams of WIC-approved

cereal over the 2-day period compared with the prorated maximum 68

grams of cereal provided in the WIC food package. There are a number of

possible reasons for this result, including that: 

(1) WIC recipients do not redeem the WIC voucher for their full amount; 

(2) Some of the WIC food purchased was either thrown out or consumed by

other members of the household; 

(3) The survey respondents underreported the amount of food consumed by

the child; 

(4) Due to imprecise means of measuring the amount of specific foods contained in some mixed dishes, some WIC-approved foods were probably

omitted from the lists of approved foods constructed for this study,

resulting in an underestimation of the amount of these foods consumed

by WIC participants; and 

26Standard errors for the estimates

presented in table 5 are not shown

because factors other than WIC status

affect consumption. For example, the

composition of the four groups differs

by age, and differences in consumption patterns across the groups may be

due largely to the fact that older children eat different foods and different

quantities of food than younger children. 

27Soft drinks accounted for over

one-third (35.4 percent) of the total

grams of other beverages.

28This analysis undercounts the percentage of calories it attributes to

WIC-approved foods, since the calories attributed to WIC-approved foods

here do not account for those WIC

foods included in food mixtures when

the dataset did not separate the calories

of component foods.
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Table 5—Average 2-day consumption of WIC-approved foods, by WIC status

Maximum 

quantity of food

Eligible Eligible in WIC food

nonparticipants nonparticipants Ineligible package

Food group All children WIC recipients non-WIC household WIC household nonparticipants (2-day average)

--------------------grams----------------

WIC-approved cereals 24.2 32.9 23.3 27.3 20.8 68

Other cereals 48.6 49.2 53.9 56.8 44.8 NA

WIC-approved juices 283.5 322.0 213.0 248.1 308.8 544

Other beverages 413.5 383.2 507.8 514.9 366.8 NA

WIC-approved milk 734.9 764.2 718.0 652.0 738.3 1,451

WIC-approved cheeses 15.2 12.6 14.2 13.0 17.8 121

WIC-approved eggs 20.7 24.5 26.4 25.4 15.6 NA

WIC-approved peanut 5.8 5.0 5.9 6.2 6.0 34

butter

WIC-approved beans/ 7.5 12.3 10.9 16.5 3.0 30

peas

--------------------calories-------------------

All WIC-approved foods 709.5 792.5 677.5 688.4 694.2 NA

All non-WIC foods 2,169.4 2,099.9 2,282.2 2,316.0 2,125.4 NA

All foods and beverages 2,878.9 2,892.3 2,959.7 3,004.4 2,819.6 NA

NA=Not applicable.
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(5) WIC recipients do not receive the maximum amounts of each WIC food,

either because the local WIC agency tailors the individual’s food package or because the child (i.e., the child’s parent) refuses to accept all of

the WIC foods offered. (Unpublished data from the Food and Nutrition

Service (FNS), the agency responsible for administering the WIC program, indicates that States are prescribing less than the maximum

amount of most WIC foods).29 In addition, the maximum amounts of all

WIC foods are not available to WIC participants. For example, cheese

is not part of the basic food package for children—it is provided only as

a substitute for milk. Similarly, WIC participants choose peanut butter

or beans/peas (but not both) as part of their food package. Thus, WIC

children can not receive the maximum amounts of both milk and cheese

and beans/peas and peanut butter.

The calculations of the average quantities of food consumed, presented in

table 5, are based on the amount of food consumed by all children in the

study. However, some children did not eat some of the specific WICapproved foods during the 2-day period in which information was collected.

Table 6 shows the percentage of children who consumed specific WICapproved foods during at least 1 of the 2 days of dietary recall. Almost all

children (98.9 percent) consumed one or more of the WIC-approved foods

during the 2-day period. However, the percentage of all children who

consumed specific WIC-approved foods varied widely, from almost 93

percent for milk to less than 9 percent for beans/peas.

Within the specific WIC-approved food groups, the percentage of children

consuming that food also varied by WIC status. For example, the

percentage of children consuming WIC-approved cereal ranged from 33.5

percent (ineligible nonparticipants) to 53.0 percent (WIC recipients). WIC

participants had the highest percentage of children who consumed a particular WIC-approved food for three of the seven WIC-approved foods. 

Regression Analysis of the Effects

of WIC Participation

The results in table 5 suggest that WIC participants consume larger amounts

of some WIC-approved foods than non-WIC children. However, factors

other than WIC status may affect the consumption of WIC foods. For

example, WIC children consume more milk than non-WIC children, but that

difference may be due to age rather than to WIC. WIC children tend to be

younger than other children, and studies show that milk consumption

declines with children’s age. Similarly, receipt of food stamps may lead to

increased consumption of some WIC-approved foods and WIC children are

more likely to receive food stamps than other children. In simple comparisons across groups, factors such as age and food stamp receipt can

confound measurement of consumption effects due to WIC. 

In order to isolate WIC-related effects, multivariate regression analysis was

used to control for observed (i.e., measured) differences between the four

groups of children. Regression analysis is a tool used to study the statistical

dependence of a variable, called the dependent variable, on two or more

other variables, called explanatory or independent variables. The technique

yields a measure of the effect of an independent variable on the dependent

29Based on data from the 2002

WIC Participant and Program

Characteristics Study.
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Table 6—Percentage of children in sample consuming WIC-approved foods during 2-day survey, by WIC status

Eligible Eligible 

nonparticipants nonparticipants Ineligible

Food group All children WIC recipients non-WIC household WIC household nonparticipants

Percent

WIC-approved cereal 37.3 53.0 31.7 45.7 33.5

WIC-approved juices 60.9 68.8 50.6 58.7 64.0WIC-approved milk 92.9 93.8 93.0 91.4 92.7

WIC-approved cheese 42.6 38.7 40.1 35.6 46.3

WIC-approved eggs 29.1 36.0 35.3 41.4 21.4

WIC-approved peanut 26.0 24.0 23.7 26.0 28.3

butter

WIC-approved beans/ 8.8 14.2 11.3 17.3 4.2

peas

Any WIC-approved food 98.9 99.0 98.8 100.0 98.8

Other cereal 54.9 45.9 59.4 47.6 56.6Other beverages 74.5 73.6 82.0 81.7 69.7Any non-WIC food 100.0 99.9 100.0 100.0 100.0Any food 100.0 100.0 100.0 100.0 100.0Note: unweighted data.
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variable, given that other independent variables are in the model. This

analysis has the benefit of simultaneously controlling for multiple factors

that may influence the consumption of WIC-approved foods, such as child’s

age, race/ethnicity, and receipt of food stamps. 

The dependent variable in nine models was the amount (in grams) of

various foods consumed by children—WIC-approved cereal, juice, milk,

cheese, eggs, peanut butter, and beans/peas, as well as other (i.e., non-WIC)

cereal and beverages. Three additional regressions were conducted for the

amount of energy (calories) consumed in all WIC-foods, in all non-WIC

foods, and in all foods (i.e., total calories consumed).30 

Table 7 lists the independent variables included in the models. The main

independent variable of interest in this analysis—WIC status—was represented by the four categories defined previously: (1) WIC participant; (2)

eligible nonparticipant in non-WIC household); (3) eligible nonparticipant

in WIC household; and (4) ineligible nonparticipant.31 In order to quantify

the qualitative WIC status, indicator (or “dummy”) variables were used, one

to represent each of the four categories. Statistically, the use of indicator

variables requires that one of the indicator variables be dropped or omitted.

In order to interpret the effect of an indicator variable on the dependent

variable, it must be compared to the omitted variable. For example, in this

analysis, the variable representing WIC participants was the omitted variable. The effect of the other three indicator variables representing WIC

status are estimated by comparing them to the omitted category. Thus, the

regression coefficients associated with each of the three groups of nonparticipants measure the effect of membership in that category compared with

the effect of membership in the omitted category, WIC participants.

Since the consumption of specific foods is influenced by many factors other

than WIC status, it is important to control for as many of these

confounding factors as possible when assessing the quantitative relationship

between WIC participation and the consumption of foods. Therefore, the

model included a number of other independent variables, representing the

characteristics of the children and their households, geographic locations,

and other factors thought to influence the consumption of food, as follows: 

Child characteristics—Variables representing the age, sex, and

race/ethnicity of the child were included to account for their effect on food

consumption patterns. A variable representing Food Stamp Program participation was included to account for that program’s effect on food

purchasing power. 

Household characteristics—Since income influences the kinds and amount

of food that can be purchased, a variable representing the annual income of

the household, expressed as a percentage of the poverty threshold, was

included. A household’s assets may affect its ability to withstand unexpected decreases in income, so two measures of household wealth were

included: homeownership and whether the household had cash assets of

more than $5,000. Size of household and whether the household was

single-headed may influence the amount of time available for meal planning

and preparation and related food choices. Number of other children 1-9

30The category “food” or “foods”

in this analysis includes beverages. 

31WIC status in this report is determined solely by current WIC participation. Previous participation in WIC

may also affect food consumption

habits, for example, through lessons

learned by a parent in WIC education

classes or from food preferences

developed while receiving WIC food

packages. However, this study does

not account for previous WIC participation, since the CSFII dataset used

for the study does not contain information on past participation in the

program. 
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Table 7—Independent variables in regression model

Variable Definition

Child characteristics:

WIC status:

WIC participant Child participates in WIC (omitted category) 

Eligible nonpart. (non-WIC household ) Eligible nonparticipating child who resides in a non-WIC household

Eligible nonpart. (WIC household) Eligible nonparticipating child who resides in a WIC household

Ineligible nonparticipant Nonparticipating child who is ineligible for WIC 

Racial/ethnic:

White White child (omitted category)

Black Black child

Hispanic Hispanic child

Other race/ethnicity Child of other race/ethnicity

Age of child:

1 year 1-year-old child

2 years 2-year-old child

3 years 3-year-old child

4 years 4-year-old child (omitted category)

Sex of child:

Male Male child

Female Female child (omitted category)

Food stamp status:

Food stamp recipient Child receives food stamps

Non-food stamp recipient Child does not receive food stamps (omitted category)

Household characteristics:

Household size Number of household members

Head's schooling Highest grade of school completed by household head

Other children Number of other children age 1-9 in household

Percent of poverty Annual household income as a percent of the poverty threshold

Household status:

Single-headed household Single-headed household

Dual-headed household Dual-headed household (omitted category)

Home ownership:

Home owner Household member owns home 

Not owned Home is not owned by a household member (omitted category) 

Household assets:

Assets of $5,000 Household has savings or cash assets of more than $5,000 

Assets less than $5,000 Household has cash assets less than $5,000 (omitted category)

Geographic characteristics:

Census region:

Northeast Household is located in the Northeast (omitted category) 

South Household is located in the South 

Midwest Household is located in the Midwest 

West Household is located in the West 

Metropolitan Statistical Area status:

Central city Household is located in a MSA, central city

Suburbs Household is located in a MSA, outside central city (omitted)

Rural Household is located in a non-MSA

Other variables:

Year of survey

1994 Survey was conducted in 1994 

1995 Survey was conducted in 1995

1996 Survey was conducted in 1996

1998 Survey was conducted in 1998 (omitted category)

Weekend days Number of weekend days of consumption data

Season:

Summer Survey was conducted during summer

Fall Survey was conducted during fall

Winter Survey was conducted during winter

Spring Survey was conducted during spring (omitted category)
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years of age was included in the model to account for the influence of other

children on the eating patterns of the child of interest. Number of years of

schooling completed by the household head was included as a proxy for

nutritional knowledge.32

Geographic characteristics—Variables based on region of residence and

metropolitan status were constructed to account for regional differences in

food consumption practices and prices. 

Other variables—Variables representing the year the survey was conducted,

the number of days of the 2 days of intake data collection that were

conducted on weekends, and the season in which the survey was conducted

were included to account for their potential effect on consumption patterns. 

In general, a single-equation model of demand for a specific food item can

be formulated and written as: 

Yi = Xi β + εi (1) 

where Yi represents a specific WIC-approved food item consumed by the

child, Xi denotes a vector of socioeconomic and geographic characteristics,

and εi represents a stochastic error term accounting for unexplained variation of the model. In many situations, the estimation of the model is

conducted using the Ordinary Least Squares (OLS) procedure. But the OLS

procedure is not valid if numerous zero values were reported for the

dependent variable Y. As shown in table 6, many children in the study did

not consume one of the types of WIC-approved food during the 2 days in

which information was collected, resulting in a large number of observations of zero. The economic interpretation of ‘zero’ consumption is

ambiguous, and consequently alternate modeling and estimation procedures

are required to conduct the investigation. The regression model used under

those circumstances is referred to as the ‘censored regression model,’ or the

‘Tobit’ model. The Tobit model is expressed mathematically by:

Y i = Xi β + ε i if Xi β + ε i > 0 (2)

Y i = 0 if Xi β + ε i < 0

The regression analysis was performed using STATA version 8, correcting

for weighting and the complex survey sample designs of the CSFII. 

Regression Results

Separate regressions were run for each of the food groups of interest. The

results of the analysis are presented in table 8.33 Regression coefficients

were considered to be significantly different from zero at p < 0.10 (i.e.,

there was less than a 1-in-10 chance of these results occurring as a random

event).34 

32In households reporting both a

male and female head of household,

the years of schooling of the female

head were used to represent the head’s

education. 

33Of the 5,519 children included in

the descriptive analysis, 12 were

dropped because they were missing

data for at least one of the independent

variables. Of the remaining 5,507

children included in the regression

analyses, 1,105 were WIC participants,

1,599 were eligible nonpartipants

(non-WIC households), 204 were eligible nonparticipants (WIC households), and 2,599 were ineligible nonparticipants. 

34Due to day-to-day fluctuations in

the dietary intake of individuals, estimates of intake based on only 2 days

of data will be distributed less tightly

around the mean than estimates based

on more days of data. This will

increase the width of the confidence

intervals around the estimate of the

mean, making it more difficult to

obtain statistically significant differences between estimates. In other

words, the presence of large intra-individual variation (day-to-day flucuations in a sample member’s reported

intake) makes it more difficult to

determine inter-individual variation

(variation in usual intake among sample members), which is the variation

of interest (Fraker, 1990). For this

reason a 10-percent threshold was chosen instead of a 5-percent threshold. 
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Table 8—Regression results

WIC cereal Other cereal WIC juice Other beverage WIC milk WIC eggs

Estimate t value Estimate t value Estimate t value Estimate t value Estimate t value Estimate t value 

Eligible nonpart. (non-WIC hh1) -48.74 -4.87 23.28 2.91 -206.64 -6.33 145.56 5.48 -23.68 -0.93 13.68 1.96

Eligible nonpart. (WIC hh1) -18.18 -1.41 8.09 0.57 -111.10 -1.9 148.37 2.52 -97.74 -1.93 2.80 0.3

Ineligible nonparticipant -47.29 -3.24 -9.42 -0.72 -146.27 -2.84 95.55 2.36 -4.12 -0.08 12.55 1.46

Percent of poverty -0.06 -0.93 0.26 4.2 0.26 0.92 -0.07 -0.31 -0.46 -2.11 -0.14 -2.96

Male 4.30 0.8 -4.80 -0.82 41.44 2.65 37.07 2.15 45.82 2.28 2.94 0.81

Age 1 year -12.32 -1.61 -20.04 -2.45 30.16 1.21 -361.57 -13.21 271.72 7.75 11.02 1.95

Age 2 years -2.91 -0.41 -1.44 -0.2 115.15 5.16 -154.41 -5.89 5.74 0.27 23.39 4.2

Age 3 years 2.25 0.34 8.63 1.94 30.01 1.27 -69.81 -2.96 -4.56 -0.28 5.05 1.07

Black 16.60 1.89 47.36 4.54 -17.57 -0.54 31.74 1 -147.38 -4.75 27.79 4.26

Hispanic 6.57 0.75 -20.54 -2.37 -35.97 -1.23 33.76 0.95 65.59 1.79 45.95 7.24

Other race/ethnicity -21.18 -2.44 -15.30 -1.36 24.17 0.5 -125.40 -2.18 9.96 0.22 29.06 4.02

Food stamp recipient -23.92 -2.5 10.46 0.97 7.84 0.25 40.05 1.31 -23.19 -0.71 1.74 0.25

Household size -3.26 -1.67 2.03 0.84 -13.57 -1.78 -5.38 -0.83 -1.98 -0.29 2.31 1.32

Single-headed household 0.88 0.1 23.51 2.48 -15.39 -0.41 5.38 0.14 -78.37 -2.54 -16.51 -2.48

Home owner 3.77 0.53 -5.12 -0.63 38.00 1.69 -10.03 -0.38 12.10 0.57 -1.84 -0.34

Assets of $5,000 -0.23 -0.04 -15.89 -2.7 0.31 0.01 -99.39 -4.62 43.03 1.69 -0.95 -0.16

Head's schooling 1.16 1.14 0.23 0.24 9.50 2.05 -16.16 -3.94 -5.41 -1.23 -2.46 -2.96

Other children 2.00 0.33 3.77 0.59 6.41 0.32 18.49 0.97 -25.13 -1.16 -13.97 -2.68Midwest -27.75 -3.65 3.92 0.56 -144.15 -3.43 107.09 2.5 8.06 0.29 -6.42 -0.77South -39.80 -6.69 19.34 2.38 -158.67 -4.08 125.07 3 -25.85 -1.06 9.98 1.2

West -18.04 -2.16 -0.02 0 -143.21 -4.26 -19.13 -0.43 -27.01 -1.01 6.30 0.75Central city 6.32 0.91 5.85 1.22 16.00 0.6 11.53 0.47 -46.98 -2.15 -7.05 -1.47

Rural -9.02 -1.84 -2.23 -0.32 -34.13 -0.73 131.66 3.07 -27.53 -0.76 -3.08 -0.45

Survey year - 1994 22.60 2.8 -18.64 -2.89 1.52 0.05 -27.46 -0.79 -64.04 -2.73 -1.77 -0.3

Survey year - 1995 22.50 2.65 -28.01 -3.09 -18.80 -0.6 40.00 1.32 -38.63 -1.07 -3.42 -0.55

Survey year - 1996 12.05 1.39 -2.64 -0.25 15.27 0.48 -49.97 -1.63 14.13 0.41 -2.82 -0.4

Weekend days -7.88 -1.66 -8.61 -1.84 -7.21 -0.4 46.98 2.65 -46.32 -2.34 5.99 1.55

Summer -5.40 -0.79 8.86 1.52 10.74 0.35 36.44 1.4 39.38 1.38 -5.59 -1.15

Fall -5.47 -0.74 10.54 1.4 15.52 0.49 -49.15 -1.26 92.58 3.6 -1.24 -0.17

Winter 11.07 1.38 -5.99 -0.84 4.06 0.12 -29.89 -0.98 -14.36 -0.47 2.66 0.47

Constant 10.11 0.47 -66.47 -2.8 197.40 2.03 503.73 5.54 878.57 9.57 -31.28 -1.4

Sigma 4.86 81.41 4.95 122.67 6.24 209.7 6.31 301.09 6.34 251 4.61 178.23

Continued—
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Table 8—Regression results—continued

WIC cheese WIC peanut butter WIC beans/peas WIC energy Non-WIC energy Total energy

Estimate t value Estimate t value Estimate t value Estimate t value Estimate t value Estimate t value 

Eligible nonpart. (non-WIC hh1) 1.78 0.59 -2.27 -0.99 -6.62 -0.46 -100.28 -4.41 94.28 1.74 -5.69 -0.1

Eligible nonpart. (WIC hh1) -1.95 -0.3 5.88 1.16 7.68 0.4 -82.64 -2.04 144.62 2.01 59.72 0.83

Ineligible nonparticipant 5.26 1.14 -4.20 -0.85 -52.49 -2.15 -79.17 -2.35 -50.83 -0.74 -131.15 -1.77Percent of poverty -0.01 -0.39 0.00 -0.13 -0.09 -0.67 -0.33 -1.99 0.42 1.38 0.11 0.32

Male -3.30 -2.1 1.27 0.78 -19.98 -2.18 47.83 3.46 135.84 5.27 183.65 5.76

Age 1 year -10.67 -4.31 -11.63 -4.65 -33.30 -2.36 146.00 6.65 -812.22 -20.70 -664.77 -15.32

Age 2 years -6.10 -2.51 -6.23 -2.44 -2.59 -0.18 20.64 1.25 -421.91 -11.15 -399.98 -10.34

Age 3 years -4.37 -1.97 0.07 0.04 -12.48 -0.82 4.93 0.3 -210.45 -6.59 -205.40 -5.65Black -12.60 -3.44 -9.32 -3.5 35.21 1.9 -67.35 -2.93 40.35 0.84 -27.59 -0.54

Hispanic -7.77 -2.23 -23.85 -7.88 191.92 12.54 43.85 2.06 -51.33 -0.96 -8.18 -0.17

Other race/ethnicity -23.30 -5.11 -19.19 -4.67 75.49 3.26 -13.50 -0.44 -169.36 2.61 -182.13 -2.62

Food stamp recipient 8.36 2.65 0.20 0.07 -12.38 -0.74 -20.49 -0.87 57.83 1.36 39.20 0.93

Household size -1.09 -1.47 -0.26 -0.4 -2.79 -0.67 -4.30 -0.82 2.82 0.20 -1.25 -0.08

Single-headed household 2.14 0.63 1.25 0.41 -17.75 -1.01 -46.29 -1.8 53.93 1.20 7.71 0.15

Home owner 0.25 0.12 0.54 0.29 14.43 1.03 14.70 0.89 0.68 0.02 15.18 0.46

Assets of $5,000 2.84 1.22 -1.16 -0.61 0.24 0.02 14.24 0.82 -39.93 0.97 -25.59 -0.56Head's schooling 1.38 2.92 0.80 1.91 -1.24 -0.77 -2.70 -0.9 3.32 0.67 0.57 0.11

Other children 4.04 1.71 2.12 1.05 -12.41 -0.86 -18.19 -1.1 38.71 1.19 19.99 0.58Midwest -4.74 -0.93 -1.69 -0.43 -11.88 -0.55 -97.66 -4.21 117.28 2.02 21.02 0.35

South -2.95 -0.73 -2.61 -0.72 49.21 2.53 -100.66 -5.17 -2.32 -0.04 -102.35 -1.96

West 4.07 0.93 1.71 0.45 6.62 0.33 -94.67 -5.47 -87.41 -1.46 -181.25 -3.11

Central city -6.67 -2.52 1.19 0.61 20.14 1.97 -31.54 -2.17 23.66 0.65 -7.87 -0.18

Rural 0.68 0.15 -0.08 -0.02 32.92 1.8 -25.33 -0.84 62.13 1.39 38.65 0.81

Survey year - 1994 -5.66 -2.37 -2.24 -0.98 -10.17 -0.6 -47.76 -2.36 -125.48 -3.33 -171.62 -3.93

Survey year - 1995 -4.79 -1.42 2.55 1 -5.17 -0.34 -24.87 -1.16 -136.99 -3.67 -161.16 -3.72

Survey year - 1996 3.96 1.05 -0.57 -0.22 28.06 1.64 21.77 0.82 -195.85 -5.35 -174.13 -5.16

Weekend days -2.55 -1.35 1.45 1.07 -16.63 -2.06 -34.99 -2.8 38.61 1.62 3.73 0.14Summer -1.18 -0.53 0.48 0.18 -8.52 -0.54 19.74 1.23 -5.58 -0.16 14.70 0.42

Fall -8.38 -2.43 -1.27 -0.51 2.68 0.14 34.53 1.7 -101.64 -3.13 -66.01 -1.92

Winter -5.35 -2.37 0.26 0.1 -9.50 -0.57 -15.72 -0.68 -68.92 -1.61 -83.66 -1.94

Constant -11.21 -1.35 -23.23 -3.74 -225.07 -5.01 957.51 17.39 2367.46 17.64 3322.39 23.23

Sigma 3.95 134.24 3.62 95.99 5.12 120.83 5.99 405.63 6.65 333.20 6.74 378.23

1hh = household

Note: Red numbers represent regression coefficients that are statistically significant at p < .10.
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WIC Status Variables

Compared with eligible nonparticipants living in non-WIC households, WIC

participants consumed significantly more WIC-approved cereal and juice

and significantly less other cereal, other beverages, and WIC-approved

eggs, holding other factors constant. Compared with eligible nonparticipants living in WIC households, WIC participants consumed significantly

more WIC-approved juice and milk and significantly less of other beverages. Compared to ineligible nonparticipants, WIC participants consumed

significantly more WIC-approved cereal, juice, and beans/peas and significantly less of other beverages.

WIC participants consumed significantly more calories from WIC-approved

foods compared with each of the three groups of nonparticipants. They also

consumed significantly fewer calories from non-WIC foods than the two

groups of eligible nonparticipants. There was no significant difference in

total calories consumed between WIC participants and the two groups of

eligible nonparticipants. Compared with ineligible nonparticipants,

however, WIC participants consumed more total calories from all foods. 

Other Variables

Many of the other independent variables included in the regression models

were also statistically significant. For example, male children consumed

significantly more calories from WIC-approved foods, non-WIC foods, and

from all foods and beverages than female children. They also drank more

WIC-approved juice, milk, and other beverages and ate less WIC-approved

cheese and beans/peas. Age of the child was also significant in several

cases. For example, relative to 4-year-olds, 1-year-old children consumed

more calories from WIC-approved foods but fewer calories from non-WIC

foods and from all foods. They also consumed more grams of WICapproved milk and eggs and fewer grams of WIC-approved cheese,

peanut/butter, beans/peas, other cereal, and other beverages. 

Participation in the Food Stamp Program was associated with increased

consumption of WIC-approved cheese and decreased consumption of WICapproved cereal. Weekend days were associated with fewer calories from

all WIC-approved foods and larger quantities of other beverages, but

smaller quantities of WIC-approved milk, beans/peas, and other cereal. 

There were numerous differences in consumption of the food groups by

race/ethnicity. For example, compared with Whites, Blacks consumed

significantly fewer calories from WIC-approved foods, less WIC-approved

milk, cheese, and peanut butter, and more WIC-approved cereal, eggs,

beans/peas, and other cereal.35 Hispanics, on the other hand, consumed

significantly more calories from WIC-approved foods than Whites, more

WIC-approved milk, eggs, and beans/peas, and less WIC-approved cheese,

peanut butter, and other cereal. There were also numerous differences in

consumption of the various food groups across geographic regions. 

Compared with the earlier years in which the survey was conducted, the

1998 survey year was associated with a significant increase in calories both

from non-WIC foods and all foods.

35Concerns about possible lactose

intolerance may account for some of

the relatively low consumption of milk

and cheese among Black children.
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Effects Associated With WIC Participation

The regression analysis discussed above identified those cases in which

WIC participants consumed significantly more or less of a type of food than

one of the three nonparticipant comparison groups. Those results were then

used to compute the marginal effect as a percent of average consumption of

WIC participants. Results are presented for the types of foods found to be

most affected by participation in WIC—grams of WIC cereal, WIC juice,

and other (i.e., non-WIC) beverages consumed, as well as total calories

from WIC-approved foods. The marginal effect associated with participation

was decomposed into two separate effects. One of these—the probability

effect—refers to WIC’s effect on the probability of consuming a particular

type of food, that is, consuming a positive amount of the food during the 2-

day period rather than none at all. As shown in table 6, during the 2-day

reference period, WIC participants were more likely to consume some types

of WIC foods than non-WIC children. The second effect is the magnitude

effect, which is WIC’s effect on the amount of food consumed by children

who ate a positive amount of the food.

WIC participants, when compared with either eligible children in non-WIC

households or ineligible children, consumed on average about 75 percent

more grams of WIC-approved cereal after other factors were held constant

(fig. 2).36 Most of this dramatic difference was due to the magnitude effect

(that is, among those children who consumed WIC-approved cereals, WIC

participants consumed larger quantities) rather than the probability effect (in

which WIC participants are more likely to consume WIC cereals). 

WIC participation was also associated with large increases (24 to 45

percent) in the WIC-approved juice consumed, depending on with which

group of nonparticipants the WIC participants were compared (fig. 3). At

Figure 2

Estimated effects of WIC on consumption of WIC-approved cereal:

WIC participation vs. three comparison groups

0

10

20

30

40

50

60

70

80

90

 Eligible 

(non-WIC households)

 Eligible*

(WIC households)

Ineligibles 

Percent of grams consumed

* Marginal effects were not reported for eligible nonparticipants in WIC households because

there was no statistical difference in the number of grams of WIC-approved cereal consumed 

between WIC participants and eligible nonparticipants.

Probability effect Magnitude effect

36Estimates of the change in consumption due to WIC participation

measured in grams for a specific commodity can be approximated by using

the figures for average consumption

for a specific commodity as reported

in table 5. For example, 75 percent

(i.e. the marginal effect) of the average 24 grams of WIC-approved cereal

consumed by all children, as shown in

table 5, equals 18 grams. 
24

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the same time, WIC participants consumed 17 to 26 percent fewer grams of

other beverages than the other groups of children (fig. 4).

With regard to calories from all WIC-approved foods, WIC participants

consumed between 11 and 14 percent more calories than children in the

other three groups (fig. 5). The probability effect was very small in all three

cases, reflecting the fact that the vast majority of children in the study

consumed some WIC-approved food during the reference period regardless

of whether they participated in WIC. On the other hand, WIC participants

consumed between 4 and 7 percent fewer calories from non-WIC foods

compared with the two groups of eligible nonparticipants. All of this

Figure 3

Estimated effects of WIC on the consumption of WIC-approved juice:

WIC participation vs. three comparison groups

0

5

10

15

20

25

30

35

40

45

50

 Eligible 

(Non-WIC households)

 Eligible

(WIC households)

Ineligibles 

Percent of grams consumed

Probability effect Magnitude effect

Figure 4

Estimated effects of WIC on the consumption of other beverages:

WIC participation vs. three comparison groups

-30

-25

-20

-15

-10

-5

0

 Eligible

(Non-WIC households)

 Eligible

(WIC households)

Ineligibles 

Percent of grams consumed

 

Probability effect Magnitude effect
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decrease in calories was due to the magnitude effect, since virtually all the

children in the study consumed some non-WIC food during the reference

period. 

Discussion

This analysis compared the consumption of WIC-approved foods by WIC

children with that of three groups of nonparticipating children—those

eligible to participate who lived in a non-WIC household, those eligible to

participate who lived in a WIC household, and those ineligible to participate. In an ideal setting, where both the observed and unobserved characteristics of WIC children differ on average from those of eligible

nonparticipants only by WIC status, the most relevant comparison by

which to isolate the effects of WIC participation is that between WIC

participants and eligible nonparticipants living in a non-WIC household.

In this analysis, that comparison showed that WIC participation was associated with increased consumption of WIC-approved cereal and juice and

decreased consumption of other cereal, other beverages, and WICapproved eggs. WIC participants consumed significantly more combined

calories from all WIC-approved foods, but significantly fewer from all

non-WIC foods. 

Thus, the results of the regression analysis suggest that after controlling for

observable differences between WIC recipients and eligible nonparticipating

children in non-WIC households, participation in WIC increases the

consumption of some WIC-approved foods while decreasing the consumption of some non-WIC foods.37 However, problems of estimation and interpretation exist if WIC recipients differ in unobservable ways from

income-eligible nonparticipants and if these differences influence nutrient

intake. Such unobservable differences, the result of possible self-selection

into the WIC program, may bias the regression estimates of WIC’s effect on

food consumption. Self-selection occurs because WIC is a voluntary

Figure 5

Estimated effects of WIC on the caloric intake of WIC-approved foods:

WIC participation vs. three comparison groups

0

2

4

6

8

10

12

14

16

 Eligible

(Non-WIC households)

 Eligible

(WIC households)

Ineligibles 

Percent of calories consumed

Probability effect Magnitude effect

37The finding that WIC children

consumed fewer grams of WICapproved eggs is unexplained. 
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program: parents choose to enroll their child. Children participating in WIC

may differ in unobservable ways from those eligible children whose parents

choose not to participate. 

Biases due to self-selection may be upward, that is, augmenting WIC’s

measured effects on the consumption of WIC foods, thereby overstating

WIC’s true impact. For example, upward selection bias may occur when

eligible children do not participate in WIC because their parents are less

knowledgeable about the importance of nutrition for a child’s health, or less

motivated to improve their child’s nutrition than parents of children who

actively seek sources of nutrition assistance. In such cases, a measured

effect for WIC may be due, wholly or in part, to parental behavior rather

than to WIC.

On the other hand, selection bias can also be downward, diminishing WIC’s

measured effects on nutrient intake, thereby understating WIC’s true impact.

This could happen if the parents of an eligible child choose not to participate because their child has low nutritional risk, with little to be gained

from WIC. Thus, WIC participants may be more likely to be at greater

nutritional risk than nonparticipants. If so, then comparisons between WIC

children and children in other groups would result in a downwardly biased

estimate of WIC’s effect. 

In an experimental study, the effects of WIC on children would be obtained

by randomly selecting from a group of eligible children, with some of them

to receive benefits and some not. On average, the characteristics (both

observable and unobservable) of the two groups of children would not differ

other than in whether they participated in the WIC program (assuming that

all children selected to receive WIC benefits did so). Differences in

consumption levels between the two groups could be attributed solely to the

effects of WIC and not to self-selection bias. However, largely due to

ethical concerns about withholding benefits from needy children, a WIC

study with a random assignment design has not been conducted. 

Although there are statistical techniques that attempt to control for selection

bias, they require that the model include one or more variables that explain

program participation but do not directly influence food consumption.

Because of the lack of such variables in the CSFII, a statistical model that

corrects for selection bias was not used in this study. However, a methodology was used that indirectly addresses possible selection bias to some

degree, specifically, with regard to a parent’s concern for a child’s nutrition

and motivation to improve it. A comparison was made between WIC participants and eligible nonparticipants living in a WIC household. Since the

nonparticipating children live in a household in which some other member

is in WIC, the household knows about WIC and is motivated enough to go

through the application process for at least one household member. When

comparing WIC participants and eligible nonparticipants in a WIC household, the study found that WIC participation was associated with increased

consumption of combined calories from all WIC-approved foods, as well as

larger quantities of WIC-approved juice and milk and decreased consumption of other beverages. This suggests once again that WIC does affect food

consumption. This result was found despite the possibility of spillover
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effects (whereby foods obtained through WIC are shared among non-WIC

members of the household), which makes statistically significant results

harder to find.

There is a caveat to this approach and its findings. The fact that some

members of the household are in WIC but other supposedly eligible

members are not raises questions as to why these non-WIC children are not

participating. One possible reason is that the child may have applied for

WIC but was prevented from participating due to the local WIC agency’s

lack of funds, in which case WIC rations participation to persons demonstrating the greatest nutritional risk.38 Although anecdotal evidence

suggests that in recent years nearly everyone who was eligible and applied

for the WIC program has been able to participate, during the years of the

CSFII survey some children may have been unable to participate due to

limited funds. Another possible reason that some eligible children in WIC

households may not participate is that they are unwilling to consume the

WIC foods (or only consume limited quantities) due to food preferences,

diminishing the parent’s incentive to enroll the child. Since the household

will already be receiving the benefits of WIC’s nutrition education program

via another member’s participation, little else will be gained by enrolling a

child who does not eat the WIC foods. In support of this second hypothesis,

results of the regression analysis indicate that compared with WIC participants, nonparticipants in WIC households consumed significantly less WICapproved milk, a major component of the WIC food package for children.39

There were no significant differences in milk consumption between WIC

participants and the other two groups of nonparticipants. 

The use of the third comparison group—children ineligible to participate

because their household income is too high—also addresses possible selection bias to some degree, specifically the issue that WIC participants may be

more knowledgeable about the importance of good nutrition than eligible

nonparticipants. Higher income households tend to have higher education

levels (and presumably more nutrition knowledge) and better diets in

general than lower income households. Thus, comparing WIC participants

with a group of ineligible nonparticipants should underestimate WIC’s effect

and make it more difficult to find significant effects from WIC participation.

However, the results of the analysis showed that when WIC participants

were compared with ineligible nonparticipants, the WIC participants

consumed significantly more combined calories from WIC-approved foods,

with larger quantities of WIC-approved cereal, juice, and beans/peas and

significantly smaller amounts of other beverages. 

Thus, participation in WIC was associated with significant increases (or

decreases) in the amount of food consumed, across the different comparision groups. Furthermore, the magnitudes of the effects associated with

WIC participation were substantial for some types of food. After controlling for other factors, participation in WIC was associated with an increase

of nearly 75 percent in the amount of WIC-approved cereal consumed

compared with eligible nonparticipants in non-WIC households and ineligible nonparticipants. Depending on the comparison group, WIC participation was associated with a 24- to 45-percent increase in the amount of

38When the lack of funds do not

allow WIC to serve all eligible persons, WIC uses a seven-point priority

system to ensure that those at the

greatest nutritional risk receive program benefits. In general, priority is

given to persons demonstrating medically based nutritional risks over

dietary-based nutritional risks, to pregnant and breastfeeding women, to

infants over children, and to children

over postpartum women.

39WIC children can receive up to

24 quarts of milk per month through

WIC.
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WIC-approved juice consumed and a 17- to 26-percent decrease in the

amount of other beverages.

The finding that WIC participants consumed significantly more of WICapproved juice and less of other beverages than all three groups of nonparticipants—as well as significantly more WIC-approved cereal than both

eligible participants in non-WIC households and ineligible nonparticipants—supports the results from previous studies in which WIC participation was associated with significantly lower intake of added sugars by

children (Siega-Riz et al., 2004; Chandran, 2003). WIC restricts juices to

those with no added sugar and sets limits on the amount of sugar in the

cereals provided through the program.

Although WIC was found to be associated with increased consumption of

some WIC-approved foods, the analysis found no statistically significant

difference in the consumption of other WIC-approved food groups such as

cheese and peanut butter, and few significant differences in the consumption

of WIC-approved milk, eggs, and beans/peas. Consumers probably have

stronger brand loyalties and taste preferences in cereals (and, to a lesser

degree, juices) than in the other WIC food groups (Kirlin et al., 2003).

However, WIC participants can only use their WIC vouchers for specific

brands of cereal that are iron-fortified and low-sugar. Cereals that do not

meet WIC requirements comprise a considerable share of the market. WIC

participants, if they want to take advantage of the free food provided by

WIC, must purchase cereal that may be different from what they would

choose if there were no restrictions. Juice may be similar in that WIC

participants are required to use their WIC vouchers on products containing

100-percent juice, which compete with other beverages in the diets of children. On the other hand, WIC regulations place fewer restrictions on the

other types of WIC foods participants can purchase with their WIC

vouchers, and there is less product differentiation among brands of milk,

eggs, dry beans/peas, etc. Thus, WIC probably constrains participant’s

choices of cereal and beverages more than choices of the other WIC foods.

So WIC participants are likely to purchase the same types of milk, eggs, dry

beans/peas, cheese, and peanut butter as non-WIC participants.40

The results clearly demonstrate that participation in WIC is statistically

associated with increased consumption of some WIC-approved foods, such

as cereal and juice. However, because of factors such as self-selection bias,

it is not possible to definitely prove that WIC participation per se is the

cause of the increased consumption of WIC foods. Even so, the finding of

similar results across three different comparison groups—eligible nonparticipants in non-WIC households, eligible nonparticipants in WIC households,

and ineligible nonparticipants—provides strong evidence that participation

in WIC, and not some confounding factor, does increase the consumption of

some WIC-approved foods. 

Given the finding that WIC participation is associated with increased

consumption of some WIC-approved foods, it is not surprising that WIC

would be associated with an increase in the energy consumption (measured

in calories) of WIC-approved foods. This study found that WIC participation was associated with an increase in the amount of total calories from all

40It should be noted that these food

types were also the most problematic

in terms of classifying specific foods

as WIC-approved due to the problems

associated with food combinations and

mixtures.
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WIC foods of 11 to 14 percent, depending on which of the three groups of

nonparticipants they were compared with. 

At the same time, among low-income children eligible for WIC, participation in WIC was associated with reduced consumption of calories from nonWIC foods (about 4 to 7 percent of the average calories from non-WIC

foods consumed by children in the study). There was no significant difference in total calories consumed by WIC recipients and the two groups of

eligible nonparticipants. This result suggests that WIC-approved foods

replace other food items in the diets of WIC participants rather than adding

to the total amount of food consumed.

WIC participants did consume significantly more total calories—an estimated 131 more calories over 2 days, which represents about 5 percent of

the average caloric intake of children in the study—compared with ineligible nonparticipants.41 However, this result does not necessarily mean that

participation in WIC leads to increased caloric consumption. As stated

earlier, these two groups—WIC participants and ineligible nonparticipants—systematically differ in many ways that cannot be controlled for and

that may confound the relationship between WIC and caloric consumption.

Thus, this report considers the more relevant comparison of the effects of

WIC participation on calories consumed to be between WIC participants

and other low-income children (i.e., the other two groups of eligible nonparticipants), a comparison that found no association between participation in

WIC and total caloric consumption.42

WIC-approved foods account for a substantial portion of children’s diets, on

average, for at least a quarter of the total calories consumed from food and

beverages. WIC accounts for an even more significant portion of younger

children’s diets—compared with 4-year-olds, 1-year-old children consumed

significantly more calories from WIC-approved foods, but fewer total calories. 

Among other notable findings, numerous differences in the consumption of

the food groups by race/ethnicity and geographic regions were found,

suggesting strong cultural and regional dietary patterns. Children’s

consumption of WIC-approved foods was also found to vary during the

week. Weekend days were associated with fewer calories from all WICapproved foods and smaller quantities of WIC-approved cereal, milk,

cheese, beans/peas, and other cereal, but with more calories from non-WIC

foods and larger quantities of other beverages and WIC-approved eggs. 

Participation in the Food Stamp Program had a limited effect on the

consumption of the individual foods included in the analysis—it was associated only with increased consumption of WIC-approved cheese, and

decreased consumption of WIC-approved cereal. This result may be

explained by the fact that food stamps can be used to purchase most foods

and beverages, including non-WIC foods, while WIC benefits are targeted

to specific types of foods (Chandran, 2003).43

An unexpected finding was that, compared with the earlier survey years of

1994-96, the 1998 survey year was associated with a significant increase in

41There was no statistical difference

between WIC participants and ineligible nonparticipants in the amount of

non-WIC foods consumed. 

42Most previous examinations of

WIC’s effects on children’s consumption of foods restricted the analysis to

low-income children. For example,

Burstein et al. (2000) limited their

analysis to children from families with

incomes less than 100 percent of

poverty; Rose et al. (1998) looked at

children from families with incomes

less than 130 percent of poverty;

Siega-Riz et al. (2004) looked at children with incomes of 185 percent of

poverty or less; and Oliveira and

Gundersen (2000) and Chandran

(2003) used a cutoff of 200 percent of

poverty. The one exception was the

descriptive study by Ponza et al.

(2004) that compared WIC participants with all nonparticipating children, regardless of income.

43Food stamps can be used to purchase most foods, except for hot

foods, foods eaten in the store, and

alcohol and tobacco.
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calories both from non-WIC foods and from all foods. Although rates of

obesity and overweight among children are increasing over time, it is

unlikely that such an increase in calories would show up in such a short

time. It is possible that procedures for collecting information on food

energy consumed in the 1998 survey differed in some way from the earlier

survey.

USDA is considering redesigning the WIC food packages and the results of

this analysis could have important implications for their future composition.

This study found that WIC has a very large impact on the consumption of

some foods such as WIC-approved cereal and juice, foods in which WIC

participants’ choices are constrained to a large degree. Furthermore, WIC

participation was found to affect the consumption of foods not included in

the WIC food package, for example, other (non-WIC) beverages. WICapproved juice competes with non-WIC beverages (such as soft drinks) in

the diets of children. 

On the other hand, WIC participation was found to have little effect on the

consumption of types of food for which WIC participants’ food choices

were less constrained, such as milk, eggs, dry beans/peas, cheese, and

peanut butter. Thus, the effect of the WIC food package on participants’

food consumption differed by type of food. This highlights the importance

of determining which foods the WIC packages should contain in order to

affect change in the dietary patterns of participants.

Numerous differences in the consumption of WIC-approved foods were also

found by race/ethnicity and geographic regions, suggesting strong cultural

and regional dietary patterns. This supports the premise that changing the

WIC food package to reflect cultural preferences may increase consumption

of certain foods. 
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Conclusions

WIC-approved foods are an important part of children’s diets, whether or

not the children participate in the program. On average, calories from

WIC-approved foods account for at least one-quarter of the total calories

from food and beverages consumed by children. To determine the effect

that participation in WIC has on the consumption of WIC-approved foods,

the consumption patterns of WIC participants were compared with those of

eligible nonparticipants living in non-WIC households. Two additional

comparison groups were constructed to account for the possibility of

spillover effects whereby WIC foods are shared among non-WIC household

members (eligible nonparticipants living in WIC households), and for the

effect of higher household incomes (ineligible nonparticipants). 

A Tobit multivariate regression analysis was conducted that took into

account the fact that some children may not consume a particular type of

food during a 2-day period. The results strongly suggest that participation

in WIC affects the consumption patterns of children, at least for some types

of foods. After controlling for other observed factors, WIC participants

consumed 24-45 percent more WIC-approved juice and 17-26 percent less

of other beverages such as soft drinks than each of the three comparison

groups. WIC participants also consumed about 75 percent more WICapproved cereal than both eligible nonparticipants living in non-WIC households and ineligible nonparticipants. The findings support results from

previous studies in which WIC participation was associated with significantly lower intake of added sugars. The analysis found little or no association between participation in WIC and the consumption of other

WIC-approved foods. 

Participation in WIC was found to result in an 11- to 14-percent increase in

the energy consumption (measured in calories) of WIC-approved foods.

However, WIC participants consumed significantly fewer calories from nonWIC foods than the two groups of eligible nonparticipants. As a result,

there was no significant difference in total calories consumed from all foods

and beverages between WIC participants and the two groups of eligible

nonparticipants. There is thus little evidence that participation in WIC

contributes to increased caloric intake among children eligible to participate.

However, relative to children ineligible to participate because their household income is too high (and who may differ from WIC participants in

fundamental, but unobservable, ways), WIC participants consumed more

total calories.

Because USDA is considering redesigning the WIC food packages, the

results of this analysis could play a role in the future composition of the

packages. This study found that although WIC participation had little effect

on the consumption of some types of food, it had a substantial impact on the

consumption of others. Numerous differences in the consumption of WICapproved foods were also found by race/ethnicity and geographic regions,

suggesting strong cultural and regional dietary patterns. This study highlights the importance of choosing the specific foods for WIC food packages

that are most likely to affect change in the dietary patterns of participants in

the program. 
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References

American Dietetic Association. Reauthorization of USDA Child Nutrition

and WIC Programs. Testimony to USDA, April 30, 2002.

Burstein, N.R., M.K. Fox, J.B. Hiller, R. Kornfeld, K. Lam, C. Price, and

D.T. Rodda. Profile of WIC Children. USDA, Food and Nutrition Service,

March 2000.

Chandran, R. “Effects of WIC Program on Food Consumption and Diet

Quality.” Paper presented at the Annual AAEA Meeting in Montreal,

Canada, July 2003. 

Fox, M.K., N. Burstein, J. Golay, and C. Price. WIC Nutrition Education

Assessment Study: Final Report. USDA, Food and Nutrition Service, Office

of Analysis and Evaluation, September 1998.

Fraker, T., S.K. Long, and C.E. Post. Analysis of the 1985 Continuing

Survey of Food Intakes by Individuals, Volume I. Mathematica Policy

Research, Inc., September 1990. 

Gordon, A., K. Lewis, and L. Radbill. Income Variability Among Families

With Pregnant Women, Infants, or Young Children. USDA, Food and Nutrition Service, Office of Analysis and Evaluation, January 1997. 

Institute of Medicine, Food and Nutrition Board. Dietary Risk Assessment

in the WIC Program. National Academy Press, Washington, DC., 2002.

Institute of Medicine, Food and Nutrition Board. Proposed Criteria for

Selecting the WIC Food Packages: A Preliminary Report of the Committee

to Review the WIC Food Packages. National Academy Press, Washington,

DC., 2004. 

Institute of Medicine, Food and Nutrition Board. Review of WIC Food

Packages: Proposal. August 19, 2003. National Academy Press, Washington, DC, 2003. 

Kirlin, J.A., N. Cole, and C. Logan. Assessment of WIC Cost-Containment

Practices: Final Report. USDA, Economic Research Service, Food and

Rural Economics Division, February 2003. 

National Association of WIC Directors. NAWD WIC Food Prescription

Recommendations. WIC Position Paper 00-001, 2000. 

National Center for Health Statistics. Health, United States, 2003, With

Chartbook on Trends in the Health of Americans. Hyattsville, Maryland,

2003.

Oliveira, V., and C. Gundersen. WIC and the Nutrient Intake of Children.

FANRR-5, USDA, Economic Research Service, March 2000. 
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Ponza, M., B. Devaney, P. Ziegler, K. Reidy, and C. Squatrito. “Nutrient

Intakes and Food Choices of Infants and Toddlers Participating in WIC,”

Journal of the American Dietetic Association, Volume 104, Number 1,

January 2004 supplement. 

Private Label Manufacturers Association. Today’s Store Brand Products

Offer Top Quality and Savings. Brochure produced for the 2000 NAWD

Convention, April 2000. 

Rose, D., J. P. Habicht, and B. Devaney. “Household Participation in the

Food Stamp and WIC Programs Increases the Nutrient Intakes of Preschool

Children,” Journal of Nutrition, Volume 128, 1998. 

Siega-Riz, A.M., S. Kranz, D. Blanchette, P.S. Haines, D.K. Guilkey, and

B.M. Popkin. “The Effect of Participation in the WIC Program on

Preschoolers’ Diets,” The Journal of Pediatrics, Volume 144, Issue 2,

February 2004. 

Tobin, James. “Estimation of Relationships for Limited Dependent Variables,” Econometrica 26 (1958).

USDA, Agricultural Research Service (ARS). Continuing Survey of Food

Intakes by Individuals 1994-96, 1998. CD-Rom. 2000. 

USDA, Food and Nutrition Service, Budget Division. Program Information

Report (Keydata), U.S. Summary, September 2003. December 2003. 

USDA, Food and Nutrition Service, Office of Analysis and Evaluation.

Summary: Fiscal Year 1998 WIC Food Package Costs, November 2000. 

USDA, Food and Consumer Service, Supplemental Food Programs Division. The WIC Foods and Food Packages, Memo, September 1997. 

U.S. General Accounting Office. The Special Supplemental Food Program

For Women, Infants, and Children (WIC)—How Can It Work Better?

Report by the Comptroller General. CED-79-55, February 1979. 

U.S. House of Representatives. House Report 107-116. Agriculture, Rural

Development, Food and Drug Administration, and Related Agencies Appropriations Bill, 2002. June 27, 2001. 
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Appendix

History of the WIC Food Packages

The 1972 legislation that created the WIC program defined the “supplemental foods” to be provided to program participants as “those foods

containing nutrients known to be lacking in the diets of populations at nutritional risks and, in particular, those foods and food products containing

high-quality protein, iron, calcium, vitamin A, and vitamin C” (P.L. 92-433).

These five target nutrients were chosen based on studies that suggested they

were lacking in the diets of the WIC target population. Legislation enacted

in 1978 removed any reference to specific nutrients by defining supplemental foods as “those foods containing nutrients determined by nutritional

research to be lacking in the diets of pregnant, breastfeeding, and postpartum women, infants, and children,” as determined by the Secretary of

Agriculture (P.L. 95-627). Although mention of specific nutrients was

removed, the WIC food packages continued to provide the original five

target nutrients since “research had not provided evidence of changes in the

dietary habits or economic situations of the target population” (44 FR

69255). The same legislation also directed the Secretary to ensure, to the

degree possible, that the fat, sugar, and salt content of the supplemental

foods is appropriate. It also allowed WIC State agencies, with the approval

of the Secretary, to substitute different foods that are nutritionally equivalent

to those in the WIC food packages, to allow for different cultural eating

patterns. The original intent of this provision was to permit areas outside

the continental United States to operate a WIC program that provides foods

indigenous to the area (44 FR 69266). However, it has received increased

attention in recent years as the WIC population has become more ethnically

diverse. 

The WIC food packages were designed to be supplemental. They were not

intended to meet all the nutritional needs of the participants, but were meant

to be used with a variety of other foods (44 FR 69255). The nutrition

education component of WIC emphasizes the need for a varied diet.

However, since USDA did not believe that nutrition education could

compensate for insufficient income, the WIC food packages were

constructed to provide high percentages of the Recommended Dietary

Allowances (RDA) for the target nutrients. In addition to their nutritional

contribution, the types of foods included in the WIC food packages were

chosen based on the following principals: cost, broad cultural and ethnic

appeal, commercial availability, versatility in preparation and use, feasibility

of apportionment into daily servings over a month’s time, and administrative feasibility (USDA, Food and Nutrition Service, 1997). The foods in the

packages are generally of domestic origin (in support of the nation’s agricultural economy) and have undergone minimal processing (FR 1994). 

Although the foods contained in the WIC packages continue to be high in

one or more of the original five target nutrients, the packages have undergone some changes. Prior to 1980, three food packages were specified for

participants: one for infants; one for pregnant, breastfeeding and nonbreastfeeding postpartum women and children; and one for children with special

dietary needs. The authorized foods contained in the packages included

iron-fortified infant formula, infant cereal, milk, cheese, eggs, iron-fortified
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breakfast cereal, and fruit or vegetable juice that contains vitamin C (44 FR

69255). The food packages were designed for group participant population

categories that consume the same general kinds of foods, with the intent that

local WIC agencies would tailor the packages to suit the nutritional needs of

the individual. However, a 1979 study conducted by the U.S. General

Accounting Office concluded that nearly all WIC participants were given

the maximum allowable quantities of the WIC foods without any attempts

to tailor the kinds and amounts of food to meet the nutritional needs of individuals (U.S. General Accounting Office, 1979). This lack of adjustment of

the packages resulted in criticism that WIC was promoting overfeeding and

encouraging waste (44 FR 69256).

In 1980, the number of food packages increased from three to six: infants 0

through 3 months, infants 4 through 12 months, children/women with

special dietary needs, children 1-5 years, pregnant and breastfeeding

women, and nonbreastfeeding postpartum women. The increase was made

to take into account the different nutritional needs of participants and the

belief that little tailoring was taking place (45 FR 74861). The food group

“dried beans/peas/or peanut butter” was added to the food packages of children and pregnant and breastfeeding women to increase food variety and

enhance the nutrient value. At the same time, the quantities of some other

foods were revised; for example, limits were placed on the amount of

cheese (to control costs as well as curb sodium levels), and a maximum

level of 6 grams of sugar per dry ounce for adult cereals was established as

a result of concern over sugar’s contribution to dental caries. 

In 1992, a seventh package—an enhanced food package for breastfeeding

women whose infants do not receive infant formula from WIC—was established to support and promote breastfeeding (57 FR 56231). The new

package added two new food items—carrots and canned tuna—along with

increased amounts of juice, cheese, and beans/peas and peanut butter, to the

items provided in the food package for pregnant and breastfeeding women.