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Women’s Health Issues 17 (2007) 84–92

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INCREASING BREASTFEEDING RATES:Do Changing Demographics Explain Them?

Alison Jacknowitz, PhD, MPP*

American University, Washington, DC

Received 20 July 2006; revised 15 February 2007; accepted 23 February 2007

Objectives: This study examines whether increases in breastfeeding rates between 1991 and2002 can be attributed to changes in the demographic characteristics of births. The demo-graphic variables investigated include maternal age, maternal education, race/ethnicity,geographic location of birth, and parity.

Methods: This study decomposes breastfeeding trends using 1991 through 2002 data from theRoss Laboratories Mothers Survey and birth certificates.

Results: Changing birth compositions by maternal age and education explain 9.8% and 11.5%of the increase in breastfeeding initiation rates, respectively. Changing birth compositions bymaternal age and education explain 10.2% and 9.0% of increasing breastfeeding rates 6 monthsafter birth, respectively. If changes in the composition of births by race/ethnicity had notoccurred, breastfeeding rates would have increased more. Changes in the composition ofbirths by geographic location of birth and parity do not explain any of the increase inbreastfeeding rates.

Conclusions: Overall, changes in the demographic characteristics of births explain up toapproximately 20% of the increasing trends in initial breastfeeding rates and breastfeedingrates 6 months after birth. Although this is a significant amount, it is important to continueinvestigating which additional factors explain recent breastfeeding increases such as changesin laws and policies, health promotion, the Special Supplemental Program for Women,Infants, and Children, employer support, technological innovation, and attitudes toward

breastfeeding.

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here are well-established short- and long-termhealth benefits of breastfeeding to children and

others. Studies in the United States and abroad haveound evidence that children who are breastfed haveower rates of urinary and respiratory tract infections,iarrhea, otitis media, bacterial meningitis, bactere-ia, and necrotizing enterocolitis (American Acad-

my of Pediatrics, 2005; Leon-Cava, Lutter, Ross &artin, 2002). Studies also suggest that breastfeeding

s beneficial for the mother’s health (American Acad-my of Pediatrics, 2005; Labbok, 2001). The list ofeneficial maternal health outcomes includes loweredisk of breast and ovarian cancers, incidence of long-erm osteoporosis, and pregnancy-induced obesity

* Correspondence to: Dr Alison Jacknowitz, American University,400 Massachusetts Ave, NW, Washington, DC 20016.

TE-mail: jacknowi@american.edu

opyright © 2007 by the Jacobs Institute of Women’s Health.ublished by Elsevier Inc.

American Academy of Pediatrics, 2005; Labbok,001).Reflecting research indicating that both children

nd mothers benefit from breastfeeding, numerousndividuals and organizations support and recom-

end breastfeeding. These individuals and organiza-ions include the US Surgeon General, Americancademy of Pediatrics, American Medical Associa-

ion, American Dietetic Association, American Acad-my of Family Physicians, and the World Healthrganization.Although researchers, public health organizations,

nd physicians generally agree on the importance ofreastfeeding, a sizable percentage of mothers do notreastfeed. In 2002, 29.9% of women in the hospitalnd 66.8% of mothers 6 months after birth did notreastfeed their children (Abbott Laboratories, 2002).

he US Surgeon General states, “The nation must

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A. Jacknowitz / Women’s Health Issues 17 (2007) 84–92 85

ddress these low breastfeeding rates as a publicealth challenge and put into place national, culturallyppropriate strategies to promote breastfeeding”United States Department of Health and Humanervices [US DHHS], 2000, p. 3). The US Governmentas selected increasing breastfeeding rates as a Healthyeople 2010 objective alongside other national healthoals such as decreasing rates of cancer, sexuallyransmitted diseases, obesity, and food insecurity. Inddition, the American Academy of Pediatrics (2005)ndorses exclusive breastfeeding (i.e., without supple-entation) for approximately 6 months after birth and

ecommends continued breastfeeding with supple-entation until the infant is at least 12 months old.Despite the fact that a share of women do not

reastfeed, the likelihood of any breastfeeding (i.e.,onexclusive) initially (i.e., in the hospital) and anyreastfeeding 6 months after birth has increased sincehe early 1990s (Abbott Laboratories, 2002). Between991 and 2002, breastfeeding rates for all mothersncreased 16.8 percentage points (31.5%) at birth and5.0 percentage points (82.4%) 6 months after birthAbbott Laboratories, 2002).

Although the literature agrees that breastfeedingates increased between 1991 and 2002 (e.g., Abbottaboratories, 2002; Ryan, 1997; Ryan, Zhou, & Acosta,002; Wright, 2001), explanations for the upwardrend have not been empirically investigated. Twoapers (Jacknowitz, 2006; Wright, 2001) offer severalossible explanations for the rising breastfeeding ratesuring this period, including changes in the demo-raphic characteristics of mothers, changes to thepecial Supplemental Program for Women, Infants,nd Children (WIC), changes in the federal govern-ent’s support and promotion of breastfeeding,

hanges in laws and policies that promote breastfeed-ng, and changes in workplace characteristics thatacilitate working and breastfeeding. However, nei-her author empirically tests these hypotheses.

This paper contributes to the breastfeeding litera-ure by studying 1 potential explanation for the up-

ard trend in breastfeeding rates that has not beenmpirically tested: changes in the demographic char-cteristics of births. Evidence suggests that the demo-raphic characteristics of births changed between 1991nd 2002. Shifts in the characteristics of births coupledith the fact that some groups of mothers are more

ikely to breastfeed than others suggests that changesn the demographic characteristics of births couldxplain the increasing breastfeeding trends. For exam-le, mothers with more education are more likely toreastfeed, and births to mothers with a college edu-ation increased 11.2 percentage points or 31.6% be-ween 1991 and 2002 (National Center for Healthtatistics [NCHS], 1993, 2003a). To examine whetherncreases in breastfeeding rates since 1991 can be

ttributed to many of the well-known demographic a

hanges in births that have been observed, this studyecomposes breastfeeding trends using 1991 through002 data from the Ross Laboratories Mothers SurveyRMS) and birth certificates.

From a policy perspective, it is most efficient toxamine the role of changes in the demographicharacteristics of births in breastfeeding trends beforemplementing policy interventions and evaluations. Ifemographic changes explain a large majority of the

ncreases in breastfeeding rates, then implementingostly programs may not be an efficient use of re-ources. Although many programs with the goal ofncreasing breastfeeding have already been estab-ished, the results from this study can be used to shapeuture breastfeeding research. If changes in the demo-raphic characteristics of births explain some of the

ncreases in breastfeeding, then it is important toontrol for these demographic factors when evaluat-ng the effectiveness of individual breastfeeding pro-

otion programs. In addition, if these changes do notxplain all of the increases in breastfeeding rates,urther research is necessary to determine which fac-ors do to ensure the continuing increase of breast-eeding rates.

ethods

atahe breastfeeding data used in this study are fromggregate tabulations of the RMS, the only dataset thatan produce annual national breastfeeding trends dat-ng back to the early 1990s. RMS, a proprietary surveyf the Ross Products Division of Abbott Laboratories,

s a large, national mail survey conducted since 1955o determine patterns of milk feeding from birth to 12

onths. Questionnaires are mailed to a probabilityample of new mothers selected from a sample framef names that represent approximately 80–85% of allational births. The list includes names from hospitalecords, county records of birth registrations, photog-aphy and diaper services, and newspapers. The sam-les are very large and have increased over time;pproximately 720,000 and 1.4 million questionnairesere mailed in 1991 and 2002, respectively. Twoapers summarize other breastfeeding data sourcesnd their advantages and disadvantages relative to theMS (Grummer-Strawn & Li, 2000; Jacknowitz, 2002).Aggregate breastfeeding estimates by maternal

haracteristic for 1991 through 2002 are from tabula-ions available in Abbott Laboratories (2001, 2002).ny breastfeeding rates at the following 2 points in

ime after birth are available to the public: initiation ofreastfeeding and breastfeeding at 6 months. The RMSsks mothers to recall the type of milk her baby wased in the hospital, at 1 week of age, in the last 30 days,

nd in the last week. In addition, mothers are asked

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A. Jacknowitz / Women’s Health Issues 17 (2007) 84–9286

bout their demographic characteristics. Breastfeedingates stratified by the following demographic charac-eristics are available: maternal age, maternal educa-ion, maternal employment, race/ethnicity, parity,

IC participation, and Census division of residence.he RMS asks whether the infant was low birth-eight, but the information is not included in the

abulations in a usable format. Tabulations only in-lude breastfeeding rates for low birthweight infantsnd all infants (including low birthweight babies);herefore, breastfeeding rates cannot be calculated foron–low-birthweight babies.Figure 1 and other studies illustrate that the annual

reastfeeding rates produced with the RMS are com-arable to those from other sporadically collectedata. Figure 1 shows breastfeeding rates from theMS, National Health and Nutrition Examinationurvey (NHANES), National Maternal and Infantealth Survey (NMIHS), National Survey of Familyrowth (NSFG), and the Food and Drug Administra-

ion’s Infant Feeding Practices Survey (FDA-IFPS).hese comparison data sources are nationally repre-entative, with approximate response rates �70% dur-ng this time period. Four of these 5 datasets provideimilar estimates of breastfeeding initiation for allothers, with the only exception of FDA-IFPS. Com-

arisons of the FDA-IFPS with the NMIHS data indi-ate that women in the FDA-IFPS sample were moreikely to be in middle- and upper-income groups,lder, married, and White than the NMIHS sampleFein & Roe, 1998). These characteristics are associated

ith higher breastfeeding rates, which is consistent

0

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70

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70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02Year

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RLMSNSFGFDA-IFPSNHANESNMIHS

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igure 1. US breastfeeding initiation rates for all mothers, 1970–002. Figure adapted from Jacknowitz (2002). Data are from theollowing sources: RLMS data are from Abbott Laboratories (2002);SFG data are from NCHS (1998, 2006); FDA-IFPS data are from

ein and Roe (1998); NHANES data are from Burstein et al. (2000);nd NMIHS data are from Visness and Kennedy (1997). NHANESnd NSFG breastfeeding initiations rates are for births over multipleears. In this figure, breastfeeding rates are assigned to the middleear in the case of an estimate over an odd number of years, thearlier year in the case of a 2-year estimate, and the second year inhe case of a 4-year estimate.

ith the higher estimates generated using the FDA- a

FPS. Studies (Hediger, Overpeck, Kuczmarski, &uan, 2001; Ryan et al., 1991) that compared breast-

eeding estimates from the RMS to those generatedsing the NHANES and NSFG also found similarreastfeeding rates among the datasets.In addition to breastfeeding statistics, data on the

omposition of births from 1991–2002 necessary toerform the analysis are from the National Center forealth Statistics’ National Vital Statistics Reports series,hich was previously titled the Monthly Vital Statisticseports series. The National Vital Statistics Reports relyn birth data extracted from 100% of birth certificatesegistered in the 50 states and the District of Colum-ia. Because these data are a near census of births forgiven year (a small fraction of births are unreported)

nd include a variety of maternal characteristics thatre available in the RMS tabulations using the sameefinitions as those used by the RMS, they are ideal tose for this study. These data are a near census owing

o a small number of unreported births. For example,n 2001, an estimated 99% of births in the United States

ere reported (NCHS, 2003b).

nalytic Approachtandardization and decomposition techniques simi-ar to those described by Das Gupta (1993) and Kita-awa (1955) are used to determine the share of the

ncrease in breastfeeding rates between 1991 and 2002hat are explained by changes in the demographicharacteristics of births. For the purposes of this study,hese descriptive techniques compare the actualreastfeeding rate with an estimated breastfeedingate for a given demographic characteristic, whichepresents what the breastfeeding rate would haveeen if breastfeeding practices remained at their 1991alues but birth rates by demographic characteristichanged. The estimated breastfeeding rate is calcu-ated holding breastfeeding rates by subgroup con-tant at their 1991 values and allowing the share ofirths for a given subgroup to change (equation 1).

BFt,S � �s�1

Nbf1991,s � brt,s (1)

n equation 1, BFt,S is the estimated breastfeeding ratehich allows the share of births by demographic

haracteristic, S, to vary to their values in year t; bf1991,s

s the actual breastfeeding rate in 1991 for subgroup s;rt,s is the proportion of births born to mothers ofubgroup s in year t; and N is the number of sub-roups for the particular demographic characteristic.or example, parity is divided into the subgroups ofirst births and higher order births. To calculate the002 estimated breastfeeding rate the following 2erms would be aggregated: 1) 1991 breastfeeding rateor first births multiplied by 2002 share of births that

re first births and 2) 1991 breastfeeding rate for

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A. Jacknowitz / Women’s Health Issues 17 (2007) 84–92 87

igher order births multiplied by 2002 share of birthshat are higher order births.

To determine the share, YS, of the increase inreastfeeding rates between 1991 and 2002 that isxplained by changes in births by a given demo-raphic characteristic, the difference between the ac-ual aggregate 1991 breastfeeding rate and the 2002stimated breastfeeding rate is divided by the changen the actual aggregate breastfeeding rates between991 and 2002. The calculation of YS for a givenemographic characteristic, S, is illustrated in equa-

ion 2.

YS �BF2002,S � bf1991

bf2002 � bf1991(2)

n equation 2, bf2002 is the actual aggregate breastfeed-ng rate in 2002 and bf1991 is the actual aggregatereastfeeding rate in 1991. Their difference is thehange in breastfeeding rates between 1991 and 2002.or breastfeeding initiation, this difference is 16.8ercentage points; for breastfeeding at 6 months afterirth, it is 15.0 percentage points. If demographichanges explain some of the increase in breastfeedingates between 1991 and 2002, then the share, YS, woulde positive. If the demographic changes explain nonef the increase in breastfeeding rates over this timeeriod, then the share, YS, would be close to zero.inally, if the changes that occurred led to lowerverall breastfeeding rates, than the share, YS, woulde negative.

emographic Characteristicshe demographic characteristics available in the RMSere included in the analysis if 3 criteria were met.

irst, the demographic characteristics were availablen both the RMS and birth certificate data and were in

usable form, which meant that the demographicharacteristic was defined in a similar manner in bothatasets and information for all subgroups was avail-ble. Second, there were sizeable differences in breast-eeding rates between mothers by this characteristic. Ififferences in breastfeeding by this factor do not exist,

hen changing the composition of births will nothange the estimated 2002 breastfeeding rate derivedn equation 1. Third, the composition of birthshanged by this characteristic between 1991 and 2002.f the composition of births has remained the samehen the estimated 2002 breastfeeding rate will bequal to the actual breastfeeding rate in 1991, thusxplaining none of the increase in breastfeeding rates.

The demographic characteristics available in bothatasets in a usable form include maternal age, ma-

ernal education, race/ethnicity, parity, and Censusivision of residence (hereafter referred to as geo-raphic location of birth). Maternal employment and

IC participation are not available in the birth certif- d

cate data and are therefore excluded from the analy-is. Questions on maternal WIC participation weredded to the live birth certificate questionnaire in003, which is after the time period of interest.To address whether differences exist in breastfeed-

ng rates between women by a given characteristic,his paper turns to breastfeeding trends and thereastfeeding literature. Jacknowitz (2002) identifiesreastfeeding correlates by graphing trends in breast-eeding practices by subgroup and conducting a liter-ture review. Studies included in the literature reviewse multivariate regression techniques to predict cor-elates of breastfeeding practices. Jacknowitz (2002)inds that of those demographic characteristics avail-ble in the RMS, maternal age, maternal education,ace/ethnicity, and geographic location of birth aretrong correlates of breastfeeding, but parity is noturing the time period of interest. Table 1 illustrates

indings for demographic characteristics that are re-ated to breastfeeding for 1991 and 2002. Younger

others are less likely to breastfeed than older moth-rs. Less educated mothers are less likely to breastfeedhan more educated mothers. Non-Hispanic Black

others are less likely than mothers of other race/thnicities to breastfeed. Mothers residing in the West-rn states (Mountain and Pacific Census regions) haveigher breastfeeding rates than other regions, whereasothers living in the East South Central division have

onsiderably lower breastfeeding rates than all otheregions.

The third criterion for determining which character-stics to decompose is whether the birth compositiony these variables changed. Table 2 illustrates that

arge changes in the shares of births occurred byaternal age, maternal education, and race/ethnicity.

etween 1991 and 2002, births to women ages �30ncreased 6.6 percentage points (21.3%) and births to

omen with a college education increased 11.2 per-entage points (31.6%). Births to Hispanic mothers,ho are more likely to breastfeed than non-Hispaniclack mothers, increased 6.6 percentage points. At theame time births to non-Hispanic White mothers, whore also more likely to breastfeed than non-Hispaniclack mothers, declined by 5.9 percentage points.lthough race/ethnicity is a strong correlate of breast-

eeding, these changes considered together suggesthat compositional changes in the race/ethnicity ofirths may not influence overall breastfeeding ratesecause, although race/ethnicity is associated withreastfeeding rates, these 2 effects may cancel eachther out. The 1 demographic variable that did notndergo compositional changes in births and is ex-luded from the analysis is geographic location ofirth.Hence, this exercise is performed for all years be-

ween 1991 and 2002 for breastfeeding initiation and

uration for maternal age, maternal education, and

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A. Jacknowitz / Women’s Health Issues 17 (2007) 84–9288

ace/ethnicity. The subgroups of maternal age at birthnclude �20 years, 20–24 years, 25–29 years, 30–34ears, and �35 years. These groups and those foraternal education and race/ethnicity are determined

y the RMS tabulations. Maternal education sub-roups include grade school, high school, non-college,ollege, and unknown. Finally, the subgroups forace/ethnicity are Hispanic, non-Hispanic Black, non-ispanic White, and other. In addition, decomposi-

ions are performed for both breastfeeding initiationnd 6 months after birth because differences in breast-eeding rates between subgroups may differ for the 2utcomes (Table 1). For example, there are largerifferences in breastfeeding initiation between moreducated and less educated mothers than in breast-eeding 6 months after birth.

Mothers with unknown education and other race/thnicity are assigned the mean breastfeeding rate forll mothers. To test whether this is a reasonabletrategy, 1991 and 2002 actual breastfeeding rates inhe hospital and 6 months after birth are compared

ith ones that weight each subgroup’s breastfeedingate by the proportion of births to that given subgroupf a demographic variable. If assigning the other andnknown subgroups the mean breastfeeding rate for

able 1. US Breastfeeding Rates by Selected Characteristics, 1991 a

Breastfeeding Rate in

1991 2002

aternal age (yrs)�20 32.2 56.220–24 45.7 66.025–29 57.8 73.430–34 65.2 76.4�35 66.7 74.1aternal educationGrade school 35.2 55.1High school 42.9 60.7Non-college 42.6 60.5College 70.2 81.2Unknown N/A N/A

ace/ethnicityHispanic 51.8 70.7Non-Hispanic, Black 25.8 53.9Non-Hispanic, White 59.2 73.4Other N/A N/A

ensus divisionNew England 55.9 73.3Middle Atlantic 48.3 65.5East North Central 48.8 66.7West North Central 56.4 73.1South Atlantic 46.4 67.5East South Central 37.5 57.0West South Central 48.4 64.9Mountain 70.0 81.0Pacific 69.5 81.5

otes: Data are from Abbott Laboratories (2001, 2002). Breastfeediace/ethnicity.

ll mothers is a reasonable strategy, we would expect o

he actual and weighted breastfeeding rates to be verylose. Indeed, the estimated breastfeeding rates (1991nd 2002 initial and 6 months after birth by maternalducation and race/ethnicity) are within 1 percentageoint of those produced by the RMS.Microsoft Excel is used to organize the data and

erform the analysis.

esults

igures 2 and 3 graph the actual breastfeeding ratesnd the estimated breastfeeding rates by year in theospital and 6 months after birth, respectively. Ifhanges in birth rates by a given demographic char-cteristic explains any of the increasing breastfeedingate, we would expect to see the estimated breastfeed-ng rates for that demographic characteristic increasever time. Therefore, the closer the estimated breast-eeding rates for a given characteristic and the actualreastfeeding rate, the larger share of the increase inreastfeeding rates that changes in the composition ofirths for that characteristic explains. Both figureshow that the estimated breastfeeding rates for mater-al education and age increase slightly and gradually

2

ital Breastfeeding Rate 6 Months After Birth

Change 1991 2002 Change

24.0 5.9 16.7 10.820.3 11.4 25.4 14.015.6 19.7 35.7 16.011.2 27.3 42.3 15.07.4 32.9 43.1 10.2

19.9 12.6 27.1 14.517.8 12.2 23.4 11.217.9 12.2 23.5 11.311.0 27.7 44.6 16.9

N/A N/A

18.9 14.8 32.7 17.928.1 6.6 19.2 12.614.2 21.0 36.0 15.0

N/A N/A

17.4 19.7 37.0 17.317.2 16.8 33.2 16.417.9 16.6 28.7 12.116.7 18.9 35.2 16.321.1 14.5 31.2 16.719.5 10.7 22.0 11.316.5 14.0 27.3 13.311.0 28.0 40.5 12.512.0 25.7 43.4 17.7

s are unavailable for mothers with unknown education or other

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ver time, suggesting that changes in the composition

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A. Jacknowitz / Women’s Health Issues 17 (2007) 84–92 89

f births by these 2 characteristics explain some of thencreasing trends in initial breastfeeding rates andreastfeeding rates 6 months after birth. In contrast,he estimated breastfeeding rates for race/ethnicityemain fairly constant over time, suggesting thathanges in the composition of births by race/ethnicityo not explain the increases in breastfeeding over this

ime period.Table 3 takes the analysis further and calculates the

hare of the increase in breastfeeding rates between991 and 2002 that changes in the composition ofirths explain. Table 3 shows that changes in thehare of births by maternal age explain 9.8% of thencrease in initial breastfeeding rates. The change inhe share of births by maternal education explains1.5% of the increasing initial breastfeeding rates. Asxpected, changes in shares of births to mothers ofifferent race/ethnicity explain none of the increase in

n-hospital breastfeeding rates since 1991. In fact,pplying the 2002 composition of births by race/

able 2. Composition of US Births by Selected Characteristics,991 and 2002

Percentage of Births

1991 2002 Change

aternal age (yrs)�20 12.9 10.8 �2.220–24 26.5 25.4 �1.125–29 29.7 26.4 �3.330–34 21.5 23.7 2.1�35 9.4 13.8 4.4aternal educationGrade school 6.1 6.0 �0.1High school 16.5 15.3 �1.2Non-college 34.9 30.7 �4.2College 35.5 46.7 11.2Unknown 7.1 1.3 �5.7

ace/ethnicityHispanic 15.2 21.8 6.6Non-Hispanic, Black 16.2 14.4 �1.8Non-Hispanic, White 63.0 57.1 �5.9Other 5.6 6.7 1.1

ensus divisionNew England 4.7 4.2 �0.5Middle Atlantic 14.2 12.7 �1.5East North Central 16.2 15.2 �1.0West North Central 6.5 6.6 0.1South Atlantic 16.7 18.0 1.3East South Central 5.7 5.8 0.1West South Central 11.5 13.1 1.5Mountain 5.9 7.6 1.7Pacific 18.6 16.9 �1.6

otal births 4,110,907 4,021,726

otes: The 1991 birth data are from NCHS (1993) and the 2002 birthata are from NCHS (2003a). The 1991 unknown education category

s primarily comprised of births from Washington and New Yorktates (excluding New York City), which did not collect educationnformation; 16,341 of the 1991 other race/ethnicity births are from

ew Hampshire, which did not collect race/ethnicity data.

thnicity to the appropriate 1991 breastfeeding rates i

esults in a lower overall initial breastfeeding rate,mplying that initial breastfeeding rates would haveeen higher if compositional changes in births byace/ethnicity had not occurred.

Similar to the findings for the initiation of breast-eeding, Table 3 illustrates that changes in the compo-ition of births explain some of the increase in breast-eeding rates 6 months after birth since 1991. The shiftf births by maternal age explains 10.2% of the in-rease in breastfeeding rates 6 months after birth. Thehanges in the birth shares by maternal educationxplain 9.0% of the increasing breastfeeding rates 6onths after birth. This statistic is approximately 2.5

ercentage points lower than the number for thenitiation of breastfeeding rates. This is because differ-nces in breastfeeding rates between the most andeast educated mothers are larger for initiation (onverage 30.2 percentage points) than duration (onverage 16.5 percentage points). Finally, changes inhe racial/ethnic composition of births account for

010

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5060

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1991 1993 1995 1997 1999 2001Year

Rate Actual

Maternal ageMaternal educationRace/ethnicity

igure 2. Decomposition of US initiation breastfeeding rates, 1991–002. Maternal age, maternal education, and race/ethnicity breast-eeding rates are calculated by weighting the 1991 breastfeeding ratey the year’s share of births to each demographic subgroup.others with unknown education are assigned the breastfeeding

ate for all mothers. Mothers with other race/ethnicity are alsossigned the breastfeeding rate for all mothers.

0

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10

15

20

25

30

35

1991 1993 1995 1997 1999 2001Year

Rate Actual

Maternal ageMaternal educationRace/ethnicity

igure 3. Decomposition of US breastfeeding rates 6 months afterirth, 1991–2002. Maternal age, maternal education, and race/thnicity breastfeeding rates are calculated by weighting the 1991reastfeeding rate by the year’s share of births to each demographicubgroup. Mothers with unknown education are assigned thereastfeeding rate for all mothers. Mothers with other race/ethnic-

ty are also assigned the breastfeeding rate for all mothers.

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A. Jacknowitz / Women’s Health Issues 17 (2007) 84–9290

ssentially none of the increasing breastfeeding rates.imilar to the case with breastfeeding initiation, ap-lying the 2002 composition of births by race/ethnic-

ty to the appropriate 1991 breastfeeding rates resultsn a lower overall breastfeeding rate 6 months afterirth.

iscussion

his paper examines whether increases in breastfeed-ng rates since 1991 can be attributed to changes in keyemographic characteristics of births. To answer theesearch question, this study decomposes breastfeed-ng trends using 1991 through 2002 data from the RMSnd birth certificate data. Findings suggest thathanges in the composition of births with respect toaternal age and education explain up to approxi-ately 20% of the upward trend in initial breastfeed-

ng rates and breastfeeding rates 6 months after birth.hanging birth compositions by maternal age andducation explain 9.8% and 11.5% of the increase inreastfeeding initiation rates, respectively. Changingirth compositions by maternal age and educationxplain 10.2% and 9.0% of increasing breastfeedingates 6 months after birth, respectively. Geographicocation of birth and parity do not explain any of thencrease in breastfeeding rates.

Changes in the composition of births by race/thnicity lead to lower breastfeeding rates in theospital and 6 months after birth. Although there is an

ncrease in the percent of births to Hispanic women,he breastfeeding rate decreases because this increases offset by a decrease in the percent of births toon-Hispanic White women who have higher breast-

able 3. Decomposition of US Breastfeeding Rates

ctual 1991 breastfeeding ratectual 2002 breastfeeding ratehange in breastfeeding rateaternal age(1) Estimated 2002 breastfeeding rate(2) Difference between actual 1991 and estimated 2002 breastfeed(3) Percent of breastfeeding increase explainedaternal education(1) Estimated 2002 breastfeeding rate(2) Difference between actual 1991 and estimated 2002 breastfeed(3) Percent of breastfeeding increase explained

ace/ethnicity(1) Estimated 2002 breastfeeding rate(2) Difference between actual 1991 and estimated 2002 breastfeed(3) Percent of breastfeeding increase explained

otes: Estimated 2002 breastfeeding rate is calculated by weighting tubgroup. Mothers with unknown education are assigned the breassigned the breastfeeding rate for all mothers.

eeding rates than Hispanic women. If the increase in t

he percent of births to Hispanic women had beenccompanied by a decrease in the percent of births toon-Hispanic Black women, the overall breastfeedingate would have increased.

Limitations of this study exist, which are primarilyata driven. First, the variables available in the RMSnd birth certificate data include the majority of keyemographic variables, but are restricted. The birthertificate data do not contain information on WICarticipation or maternal employment. In addition,

he aggregate RMS data do not stratify breastfeedingates after breastfeeding by birthweight status. How-ver, none of these variables are likely to explain thencrease in breastfeeding trends over the time periodf interest. WIC participation among eligible infantsas increased (United States Department of Agricul-

ure, 2006); however, evidence suggests that WICarticipation is negatively related to breastfeedingractices (Bitler & Currie, 2005; Ryan & Zhou, 2006).urther, maternal employment rates among womenith young children �3 have increased (United Statesepartment of Labor, 2006) and studies indicate thataternal employment is negatively related to breast-

eeding (Jacknowitz, 2002). The research on the rela-ionship between low birthweight status and breast-eeding is mixed between detecting no relationshipetween the 2 variables and a negative relationshipe.g., Chatterji & Brooks-Gunn, 2004; Ryan & Zhou,006). However, even if the relationship were nega-ive, with an increasing percent of low-birthweightnfants (NCHS, 2003a), this demographic characteris-ic would not explain the increase in breastfeedingates.

The second primary limitation of the study is that

Breastfeeding Rate

In Hospital Six Months After Birth

53.3 18.270.1 33.216.8 15.0

54.9 19.7tes 1.6 1.5

9.8 10.2

55.2 19.5tes 1.9 1.3

11.5 9.0

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A. Jacknowitz / Women’s Health Issues 17 (2007) 84–92 91

ethods that account for the associations between thendependent variables such as changing the demo-raphic characteristics sequentially or using multivar-

ate regression analysis. For example, maternal age atirth and maternal education at birth are likely corre-

ated as more educated women tend to have childrenater in life. Hence, the estimate of 20% of the increasen breastfeeding explained by maternal education andge is overestimated as a result of this positive corre-ation. A final limitation is that, although breastfeed-ng rates from the RMS are comparable to those fromther nationally representative datasets, they repre-ent 80–85% of births or fewer depending on theesponse rate for the year. Thus, the breastfeedingates are not completely comparable to the birth data,hich represent a near census of US births.Although there are limitations, this study does

ontribute to the literature by starting to investigatehe factors that explain recent trends in breastfeedingractices. Given the health benefits of breastfeeding tooth mothers and children, it is important to identifynd understand the factors explaining these increasingreastfeeding rates to ensure their continued growth.lthough this study does explain a sizeable share of

he increase in breastfeeding rates, it is important toontinue investigating which additional factors ex-lain recent breastfeeding increases. Plausible factors

o investigate include changes in laws and policies,ealth promotion, the WIC Program, employer sup-ort, and technological innovation. A final promisingxplanation for the increasing breastfeeding trends ishanges in attitudes toward breastfeeding practices.

Given that changes in the demographic composi-ion of births do not explain the majority of thencrease in breastfeeding trends, it is worthwhile toursue and evaluate current and additional pro-rams to improve breastfeeding. However, the find-

ngs do highlight the importance of controlling foremographic variables when examining the effectsf programs to improve breastfeeding rates afterreastfeeding. Finally, the study does raise the issuef the importance of considering whether demo-raphic changes influence health behaviors beforeonsidering new policies and programs. If demo-raphic changes do explain a majority of trends in aealth behavior, the implementation of an interven-

ion may not be an efficient use of resources.

cknowledgmentsthank Julie DaVanzo, Steven Haider, Rebecca Kilburn,

lizabeth Peters, and Robert Schoeni for helpful comments;teven Putansu provided excellent research assistance. Fi-ancial support from the RAND Graduate School Hagopianissertation Award is gratefully acknowledged. This work

eflects only the opinions of the author.

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uthor DescriptionAlison Jacknowitz, PhD, MPP, is an Assistant Pro-

essor of Public Administration and Policy at Ameri-an University. Her interests include child and familyolicy, child well-being, poverty, and public assis-

ance programs. She has written several papers on theopic of breastfeeding including examining the effectsf welfare work requirements and workplace charac-

eristics on breastfeeding decisions.