The USDA encourages people to eat a variety of fruits and

vegetables through the Food Guide Pyramid and participation in the National 5 A Day Partnership. A varied diet helps

ensure a complete mix of nutrients, and a lack of variety in

vegetable consumption has been further linked to the incidence of obesity (e.g., McCrory et al.). To assist these

efforts, the USDA’s Economic Research Service has investigated the factors that influence the purchase of vegetables,

and identified obstacles to variety. These obstacles stem

both from a household’s level of spending on vegetables

and its demographics. Social marketers and nutrition 

educators could use this information to better tailor their

message, or determine whether any one group of consumers

needs to be targeted. 

What Determines Variety?

Social marketers behind the 5 A Day campaign have long

encouraged households to allocate more of their food dollar

to fruits and vegetables, and it is likely that these efforts are

already encouraging variety. A number of economic studies

have found a positive relationship between a household’s

expenditures on food and the variety of foods purchased. 

If a household’s expenditures on vegetables are likely to

affect the variety of its purchases, then so too are a household’s income and demographic characteristics. Higher

income households spend more money on fruits and vegetables, as do households with members who are older and

who have a college education (e.g., Blisard et al.).

However, demographics could have a more direct impact

on variety. Regardless of how much is spent on vegetables,

we might expect differences in variety due to households’

race and ethnicity, the number of people living in the

household, or age and education. Suppose a homemaker is

preparing a meal for his or her spouse and their children.

United States

Department of

Agriculture

Economic 

Research

Service

Agriculture Information Bulletin Number 792-3 October 2004

What Determines the 

Variety of a Household’s

Vegetable Purchases?

Hayden Stewart, hstewart@ers.usda.gov, 202-694-5394

J. Michael Harris, jharris@ers.usda.gov, 202-694-5386

Joanne Guthrie, jguthrie@ers.usda.gov, 202-694-5373

Through the Food Guide Pyramid and participation in the

National 5 A Day Partnership, the USDA encourages the 

consumption of a variety of fruits and vegetables.

Bread, Cereal,

Rice, & Pasta

Group

6-11

SERVINGS

Fru

Group

2-4 SERVINGS

Meat, Poultry, Fish,

Dry Beans, Eggs,

& Nuts Group

2-3 SERVINGS

Source: U.S. Department of Agriculture/U.S. Department of Health and Human Services

Vegetable 

Group 

3-5 SERVINGS

Milk, Yogurt,

& Cheese

Group 

2-3 SERVINGS

Food Guide Pyramid

A Guide to Daily Food Choices

Fat (naturally occurrin and added)

Sugars

(added) 

These symbols show fat and 

added sugars in foods.

Fats, Oils, & Sweets KEY

USE SPARINGLY
The dish being prepared can be served with three different

vegetables— potatoes, corn, and carrots. All members of

the household like potatoes. However, at least one child

dislikes corn, while another dislikes carrots. Does this

homemaker tend to serve all three items, so that everyone

in the household can have everything they like? Or does

this homemaker tend to serve only potatoes because that

item is agreeable to everyone?

How We Measured Variety

The annual purchases of 6,344 households at retail food

stores in 1999 were examined. These marketing data

allowed us to identify purchases corresponding to each of 24

types of vegetables: artichokes, asparagus, broccoli, brussel

sprouts, cabbage, carrots, cauliflower, celery, corn, cucumbers, eggplant, iceberg lettuce, green beans, lettuces (other

than iceberg), mushrooms, onions, peas, potatoes (other than

sweet potatoes), radishes, spinach, squash, sweet potatoes,

sweet peppers, and tomatoes. Each of these 24 types may

include frozen, fresh, and canned items. For example, we

identified purchases of spinach in all three forms, but iceberg lettuce was observed in only one form, fresh. 

Variety was next defined over a full year of purchases for

each household in two ways. First, we counted how many of

the 24 different types of vegetables a household had bought.

Second, we used a Simpson index to measure how evenly a

household had spread its servings across all 24 of these types.

The Simpson index assigns a lower score to households concentrating more of their purchases on only one or two vegetables. Thus, each measure of variety tells a different aspect

of the same story. Suppose two households had each 

purchased one or more servings of each of 10 types of vegetable. By our first measure of variety, the two households

have an equally diverse diet. Further suppose, however, that

one household had purchased 100 servings of each of the 10

types, while the other had bought 900 servings of just one

type, and only a few servings of each of the other nine. The

Simpson index would assign a score of about 0.90 to the

household allocating an equal quantity share to each type of

vegetable, and a score of about 0.20 to the household concentrating most of its purchases on just one type of vegetable. 

Finally, a two-step statistical model was estimated. In the

first step, we explain a household’s level of spending on

vegetables as being dependent upon its income and various

demographic characteristics. In the second step, we further

demonstrate how a household’s variety of purchases

depends upon its demographic characteristics, holding fixed

the household’s level of spending from the first step. A

more complete description of this model is provided in a

forthcoming article in the Review of Agricultural

Economics by H. Stewart and J.M. Harris, “Obstacles To

Overcome in Promoting Dietary Variety: The Case of

Vegetables.”

Expenditures Are Critical

If social marketing campaigns can encourage households to

spend more money on vegetables, then our statistical analysis suggests that they may already be encouraging households to buy a wider variety of vegetables. Households

spent $56 per person per year, on average, to buy 13 of our

24 types of vegetables. If social marketers could induce the

typical household to double its spending to $112, we would

expect this household to buy 3 or 4 more types of vegetables. Similarly, we would expect the same household to

score 32 percent higher on the Simpson index. In 1999, only

12.5 percent of households spent $100 or more per person

per year.

2 Economic Research Service / USDA

Agriculture Information Bulletin 792-3

Households spent $56 per 

person per year, on average,

to buy 13 of our 24 types of 

vegetables.
Income was found to be important to variety, because a

household’s income affects its vegetable expenditures. For

example, an increase of 10 percent in a typical household’s

income is associated with spending 2.5 percent more on

vegetables. 

A number of demographic factors are also found to influence a household’s expenditures on vegetables. For example, an increase of 10 years in the age of a household’s head

is expected to raise that household’s annual, per-person

spending on vegetables by about $8.33 (an increase of

about 15 percent for the typical household).

The relationship between variety and spending for vegetables is nonetheless an imperfect one. For example, one surveyed household spent $231.38 on vegetables in 1999. They

bought 2.5 servings of carrots, 2 servings of onions, and

652 servings of potatoes (mostly frozen). While this example is admittedly extreme, our findings about the direct

effects of demographics on variety help to explain this sort

of behavior. 

Demographics Are Key to Variety

For any level of spending on vegetables, the number of people living in a household affects the variety of that household’s purchases. In fact, variety of purchases increases if a

second person is added to a single-person household, probably because both people are exposed to foods enjoyed by

the other. A different picture emerges as more people are

added to the household, however. Variety will decrease if an

additional person is added to a household with five or more

members. This is somewhat surprising. Because they eat

out less often and buy fewer convenience foods, larger families are a prime market for basic food ingredients, which

include vegetables. One possible explanation is that homemakers in larger households have greater difficulty producing meals with vegetables that all members of their household find acceptable.

Consistent with the above, if one or more members of a

household are children, the household is likely to purchase

one fewer type of vegetable. This finding is consistent with

the possibility that children are most likely to protest the

presence of certain vegetables on the dinner table.

Youth can also limit variety. Compared with a household

headed by a 50-year old, a household headed by a 30-year

old is expected to buy one fewer type of vegetable and

spread out its servings of vegetables 5 percent less evenly,

as measured by the Simpson index.

Education may promote variety. A household with a college-educated head is expected to buy slightly more types

of vegetables than an otherwise identical household whose

head has not completed college.

Households likely to cook more meals from “scratch” also

appear to buy a more varied mix of vegetables. If a household spends 10 percent more of its at-home food dollar on

39 basic cooking ingredients other than vegetables (e.g.,

cooking oil, flour, and sugar), that household scores 4.1 percent higher on the Simpson index. 

Economic Research Service / USDA 3

Agriculture Information Bulletin 792-3

Variety increases with the size of a household up to 

a point, and starts to decrease thereafter

Source: Economic Research Service.

123456 0

2

4

6

8

10

12

14

16

18

Variety (number of types purchased)

Number of household members

NoteVariety of purchases was simulated by holding all ariables 

at their sample mean except for a household's size

imilar results apply if ar iety is measure by the impson inde x
Finally, race and ethnicity are important. As measured by

the Simpson index, Asian and Hispanic households spread

out their vegetable purchases 23 percent and 6.5 percent

more evenly than White, non-Hispanic households do. 

Implications for Social Marketers

Encouraging households to allocate more of their food dollar to vegetables may be a reasonable starting point for promoting variety. Still, social marketers may want to add

strategies for overcoming obstacles associated with demographics. For instance, returning to our simple example of a

homemaker preparing a meal for his or her spouse and their

children, the typical homemaker may serve only the potatoes to negate the competing preferences of different household members. To overcome this sort of problem, social

marketers might suggest offering a raw vegetables platter

from which each household member can take what they

like, exposing all members to a variety of foods without

limiting the choices available to others. Another strategy for

social marketers to consider might involve exposing children to a wider variety of vegetables through ethnic dishes.

Asian and Hispanic diets appear richer in variety than those

of other ethnic groups.

Information Sources

Blisard, N., H. Stewart, and D. Jolliffe. “Low-Income

Households’ Expenditures on Fruits and Vegetables.”

Washington DC: U.S. Department of Agriculture,

Economic Research Service. Agricultural Economic Report

No. 833, May 2004.

McCrory, M.A., P.J. Fuss, E. Saltzman, and S.B. Roberts.

“Dietary determinants of energy intake and weight regulation in healthy adults.” Journal of Nutrition 130(2000):

276-279.

Stewart, H., and J.M. Harris. “Obstacles To Overcome in

Promoting Dietary Variety: The Case of Vegetables.”

Review of Agricultural Economics (Spring 2005).

4 Economic Research Service / USDA

Agriculture Information Bulletin 792-3

Relative to White, non-Hispanic households, 

Asian and Hispanic ones purchase more variety, 

Black households buy fewer types of vegetables, 

but spread out their purchases more evenly across 

what they do buy 

ource conomic esearch erice

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