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Food Consumption and Nutrition Division, International Food Policy Research Institute, Washington, DC 20006 and * Programa de Asignación Familiar, Colonia Palmira, Tegucigalpa, Honduras
2To whom correspondence should be addressed.
| ABSTRACT |
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KEY WORDS: nutrition programs targeting Honduras impact measures children
| INTRODUCTION |
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Although much has been written about the targeting of poverty
alleviation programs in Latin America (Grosh 1994
), the
expected benefits of targeting nutrition interventions are less well
understood. In particular, there is very little evidence that can be
used to assess the extent to which malnutrition clusters within
subnational regions, communities or even households. It is a truism
that geographical targeting is likely to be successful only when the
divisions selected are both internally homogeneous and highly
differentiated one from another. On the other hand, if administrative
costs are to be kept from swamping the entire program budget,
household-or individual-level targeting would probably require
identifying indicators that could adequately predict malnutrition at
the household level without requiring repeated anthropometric
assessments of individual children.
In this paper, we examine the potential gains associated with different types of administrative targeting of large-scale nutrition interventions in Honduras. The magnitude of such gains can be evaluated a priori in Honduras because of the existence of regularly updated national censuses of the nutritional status of first-grade school students, which permit the accurate determination of the prevalence of malnutrition at a local level. We take the most recent of these censuses as a "baseline" scenario against which we assess the potential gains from a variety of large-scale, hypothetical nutrition interventions. Specifically, for each intervention, six different approaches to beneficiary targeting are simulated, ranging from the random selection of beneficiaries through to perfect individual-level targeting. Methods for assessing effect are adapted from the economics literature because standard nutritional measures are highly insensitive to changes of a level conceivable in a program context.
| SUBJECTS AND METHODS |
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Data recorded in the 1997 Census included school identity, type
(government vs. private) and location, and the birth date, height, sex
and grade repetition status of each child. Height measurement was
carried out by the regular schoolteachers, using a standardized
methodology. For the purposes of the current analysis, age- and
sex-standardized measures of height were calculated using the
National Center for Health Statistics (NCHS) growth reference
(Hamill et al. 1977
). The sample sizes in the current
analysis differ somewhat from the published report of the Census
results. This is because all children with dates of birth between Jan
1, 1985 and December 31, 1991 were included in this analysis, assuming
an interview date of March 4, 1997 (the modal date) where this was not
recorded. Children (n = 1980; <1%) with
height-for-age Z-scores (HAZ) outside the permissible range of -6
to + 4 were excluded, as were the approximately one fifth of children
who were repeating first grade rather than being first-time
enrollees. It was considered that these children were highly select,
could not be deemed representative of all children in their school
catchment areas and probably should not have been included in the
Census in the first place if the intention was to approximate
population-based indicators. The final sample for analysis was
therefore 191,110 children, distributed among 8014 schools, in 297
municipalities (municipios) and in 18 departments
(departamentos).
Even after standardizing measured heights using the NCHS reference, it was still considered problematic to compare rates of malnutrition across locations because of a complex of the following three factors: 1) children of markedly different ages ranging from 62 to 146 mo were included in the sample; 2) there were systematic differences in the age profiles of these children from one location to another; and 3) older children had systematically lower HAZ in this population. To the extent that nutritional status does routinely deteriorate with age between 62 and 146 mo in Honduras, areas with delayed enrolment will appear to have worse nutritional problems because the children in first grade are relatively old. To address this problem, the measures were restandardized by using a polynomial linear regression model to estimate the empirical relationship among HAZ, age and sex, and by adding the residual from this model to the predicted value for a male child aged exactly 7 y. This procedure resulted in a <0.5% reduction in the overall national prevalence of stunting (HAZ less than -2), but did alter the ranking of the 18 departments, specifically those in the middle of the distribution.
The analysis of the potential of targeted interventions to reduce the
prevalence and severity of malnutrition (stunting) was based on three
different measures. The first of these,
P0, is the prevalence of stunting,
which is calculated as follows:
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where i indexes the child and
xi takes the value 1 when the childs
HAZ is less than -2, and 0 otherwise. Although this measure is widely
used to evaluate the effect of nutrition interventions, it is highly
sensitive to small changes around the threshold value of -2 and at the
same time not at all sensitive to large changes occurring at lower
values. For the purposes of impact evaluation, this is undesirable
because a change from -4 to -2.5 Z-scores is of much greater
functional significance than a change from -2.1 to -1.9 Z-scores.
In many respects, a better measure is the malnutrition gap,
P1, which can be interpreted as a per
capita measure of the total shortfall of individual HAZ below the
threshold value of -2; it is the sum of all shortfalls divided by the
population, calculated as follows:
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where zi = HAZ if HAZ is less than -2, and zi = -2 if HAZ is -2 or greater.
Thus, by way of illustration, P1
increases by a quantity equal to 2/n for each child with HAZ
= -4, by 0.5/n for each child with HAZ = -2.5
and by 0 for each child with HAZ = 1. Our final measure,
P2, is referred to as the
quadratic malnutrition gap; it is similar to
P1 except that the difference between
a stunted childs Z-score and the threshold value of -2 is
squared before averaging over the population. The measure is calculated
as follows:
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where zi = HAZ if HAZ is less than -2, and zi = -2 if HAZ is -2 or greater.
Thus P2 increases by a quantity equal
to 4/n for each child with HAZ = -4, 0.25/n
for each child with HAZ = -2.5 and 0 for each child with HAZ
= 1. This means that improvements in the Z-scores of severely
malnourished children are weighted much more heavily than comparable
improvements for the marginally malnourished. The three measures,
P0,
P1 and
P2, are adaptations of a series of
poverty measures familiar to economists as the Foster-Greer-Thorbecke
poverty measures (Foster et al. 1984
).
For this analysis, we assume initially that a nutrition program can be
implemented that would achieve a coverage of 20% of all children
nationwide. Although this is clearly ambitious, it is consistent with
the current policy framework being implemented in Honduras [see, for
example, Interamerican Development Bank (1998)
]. We
further assume that the hypothetical program would result in all
beneficiary children registering an improvement of 0.5 Z-scores of
height-for-age. We recognize that such a large effect would actually be
difficult to achieve in a program context, given that continuous
supplementary feeding from 0 to 36 mo resulted in cumulative effects at
36 mo of <1 Z-score of length-for-age in a small, carefully
controlled, randomized trial in Colombia (Lutter et al. 1990
). However, for this analysis, we consider it important to
evaluate the potential impact of a highly effective intervention.
Finally, we assume that program nonbeneficiaries are unaffected by the
program, and that factors external to the program affect beneficiaries
and nonbeneficiaries in equal measure. We then simulate six different
targeting strategies as follows: 1. Perfect
targeting. Beneficiaries are the C% of children with the
lowest preintervention HAZ (where C is equal to the program
coverage). Perfect targeting is, of course, impossible in a program
context because it requires constant monitoring of child anthropometric
status. It is included in our analysis purely for comparative
purposes. 2. Individual targeting using an imperfect
screening indicator (proxy). A proxy indicator is developed for which
50% of the total variance is explained by true HAZ and the remaining
50% is random noise. Beneficiaries are the C% of children
with the lowest scores on this proxy indicator. Such an approach might
be effected by identifying a set of household-level variables that
are highly correlated with child anthropometric status, and then
conducting a rapid census of all households in the country and scoring
their risk level on the basis of these
indicators. 3. Targeting by school. Beneficiaries are the
children attending schools with the lowest mean preintervention
Z-scores. 4. Targeting by municipality. Beneficiaries are
the children living in municipalities with the lowest mean
preintervention Z-scores. 5. Targeting by
department. Beneficiaries are the children living in departments with
the lowest mean preintervention Z-scores. 6. Untargeted.
Beneficiaries are a random C% selection of children. This
situation, or something similar, might arise in the case of a program
with selection criteria totally uncorrelated with child anthropometric
status.
To test the sensitivity of the results to different assumptions about the magnitude of the intervention effect and the coverage of the program, all analyses were repeated with intervention effects ranging from 0.0 through to 0.5 Z-scores gained per beneficiary, and program coverages of 10, 20 and 30%.
Parents in Honduras are fully aware that their childrens heights will be determined and recorded during the course of the school year. The current research thus complies with the Helsinki Declaration as revised in 1983.
| RESULTS |
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Table 1
shows the effect on the prevalence of stunting
(P0) of a program with a 20% coverage
rate and gains of 0.5 Z-scores for all beneficiary children, using
six different approaches to targeting. By design, program coverage was
virtually identical, regardless of the method of targeting used. The
most striking result of this analysis was that perfect targeting would
leave the prevalence of stunting in Honduras completely unchanged. This
is because all of the 20% of children with the lowest HAZ have
preintervention values below -2.5, and would thus fail to exceed the
-2 threshold even if they gained the full 0.5 Z-scores as a result
of the program. All other targeting mechanisms, including random
selection of beneficiaries, were associated with better outcomes
because some children with preintervention Z-scores in the range
-2.5 to -2.0 were included. Individual targeting using a proxy
indicator with equal parts noise and information, and geographic
targeting by school, municipality or department were all associated
with similar outcomes, with the rate of stunting showing a decline from
42.1 to 38.538.6%. Random selection of beneficiaries was minimally
less effective.
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Table 2
shows the effect of the hypothetical program on the severity of
malnutrition as measured by P1 (the
malnutrition gap) and P2 (the
quadratric malnutrition gap). Perfect targeting reduced the
malnutrition gap from 0.355 Z-scores to 0.255 Z-scores. This
follows logically from the fact that 20% of all children, all of them
initially stunted, gained 0.5 Z-scores as a result of the program,
whereas the remainder were unaffected, giving an average gain of 0.2
x 0.5 = 0.1 Z-scores for the whole population. In
relative terms, this scenario leads to a reduction in the malnutrition
gap of 28.1%. Geographic targeting was less effective, leading to
reductions of 14.8% (targeting by department, the least effective
geographic strategy) to 18.6% (targeting by school, the most effective
strategy). With respect to effect on the malnutrition gap, there was
virtually no difference between targeting by municipality and targeting
by department. Individual targeting using a 50%-noise proxy indicator
was somewhat more effective than the most effective geographic
targeting; this was associated with a 21.2% reduction in the
P1 measure. As expected, random
selection of beneficiaries resulted in the lowest effect (a 9.5%
reduction in P1).
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Sensitivity of results to different assumptions about the coverage and effectiveness of the intervention.
To determine the generalizability of the findings reported above to
situations in which the intervention was less effective (resulted in a
<0.5 Z-score gain for program beneficiaries), or achieved greater
or < 20% coverage, all analyses were repeated for a range of
different assumptions. Figure 1
shows that for the case of individual targeting using an imperfect
screening indicator, increasing the effectiveness of the intervention
(from 0 up to 0.5 Z-scores gained per beneficiary) was associated
with an almost perfectly linear increase in effect, measured as the
percentage reduction in malnutrition (any measure). This linear
association between the effectiveness of the intervention and program
effect was in fact observed for all six targeting strategies,
regardless of program coverage (data not shown). Figure 2
shows the reduction in malnutrition (each of the three measures)
associated with individual targeting using an imperfect screening
indicator, at three different levels of program coverage and assuming
in each case a program-induced gain of 0.5 Z-scores per
beneficiary. Some nonlinearity was observed, so that there are
increasing returns to scale when effect was measured as the prevalence
of stunting, but decreasing returns to scale when the effect measure
chosen was more sensitive to changes in the severity of malnutrition
(malnutrition gap or quadratic malnutrition gap). The same pattern was
observed at lower levels of intervention effectiveness (data not
shown). However, when a less effective targeting strategy such as
large-area geographic targeting was adopted, the association
between coverage and effect approached linearity. This is illustrated
in Figure 3
, which shows the reduction in malnutrition associated with geographic
targeting at the department level, at three different levels of program
coverage and assuming gains of 0.5 Z-scores per beneficiary in each
case.
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| DISCUSSION |
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In this paper, we propose two novel measures of effect for
population-based nutrition interventions, based on the
Foster-Greer-Thorbecke poverty measures (Foster et al. 1984
). The first of these measures, which we call the
malnutrition gap, can be interpreted as a per capita measure
of the total shortfall of individual HAZ below the threshold value of
-2. This measure values equally a child moving from -4 Z-scores
to -3.5 Z-scores and another moving from -2.5 to -2, but
disregards changes above the threshold value of -2. The second
measure, which we call the quadratic malnutrition gap,
overweights gains among the severely malnourished relative to similar
gains among the moderately malnourished. We find this measure to be
more consistent with the epidemiologic literature on the associations
between poor anthropometric status and health outcomes. This literature
clearly indicates that a child at -4 Z-scores is far more likely
to die than one at -2.5 Z-scores (Pelletier 1994
).
We find that a perfectly targeted program with 20% coverage and 0.5
Z-score gains would reduce the malnutrition gap by >28% and would
reduce the quadratic malnutrition gap by nearly 50%. We recognize,
however, that perfect targeting is not a realistic option for nutrition
programs because of the expense of screening, the rapid evolution of
nutritional status in young children and the fact that such a system
creates incentives for parents to withhold food and other resources
from their children in order to qualify for the program benefits. At
best, then, a system of individual screening would be based on
indicators of vulnerability to stunting, which might or
might not correlate highly with achieved nutritional status. We have
simulated a proxy indicator of vulnerability that is highly correlated
with actual nutritional status because 50% of the total variance in
the proxy measure is explained by true status (equivalent to a
correlation of r = 0.71). If our hypothetical program
were implemented using this proxy indicator for targeting, the
malnutrition gap would be reduced by 21% and the quadratic
malnutrition gap by 32%. These effects are (predictably) lower than
those that would result from perfect targeting, but it is very likely
that this reduction would be justified by substantially lower
administrative costs. Our recent experience in Honduras would suggest
that implementing a screening tool based on proxy indicators would cost
US$10/household. This cost is based on a single application of a
two-page questionnaire, with 15 questionnaires completed per
enumerator per day and one supervisor (plus one cartographer) to every
four enumerators. With a total of approximately one million households
in Honduras, the screening cost-effectiveness ratio using
household-level indicators would be <US$500,000 per percentage
point decrease in the malnutrition gap, or US$312,500 per percentage
point decrease in the quadratic malnutrition gap (again assuming 20%
program coverage and a 0.5 Z-score gain for all beneficiaries).
Geographic targeting is logistically simpler than individual targeting and also reduces the costs of program implementation. In this analysis, we have shown that targeting by school could lead to a 27% reduction in the P2 measure of the severity of stunting, which we feel would be a very significant achievement in a country such as Honduras. In addition, it is only slightly lower than the benefit expected with individual targeting by proxy indicator. Targeting by municipality or by department would be associated with somewhat lower benefits, whether measured by P1 or P2. We believe that a school height census provides sufficient information to implement municipality-level (or department-level) targeting. The total cost of the 1997 school height census was <US$40,000, implying that for municipality-level targeting, the screening cost effectiveness ratio would be only US$2532 per percentage point decrease in the malnutrition gap, or US$1843 per percentage point decrease in the quadratic malnutrition gap.
It is interesting to note that in Honduras, targeting at the municipality level appears to be no more effective than targeting at the department level, regardless of the criterion used to quantify effect. Targeting at the school level does appear to be more effective, but this higher potential effect must be weighed carefully against the greater costs of delivering a program targeted at the school rather than at the department level, i.e., the 2514 schools selected under the former strategy (assuming 20% coverage) are distributed across 17 of the 18 departments in the country, compared with just 5 under the department-level targeting scenario. Furthermore, the school-level estimates derived from the school height census are in some cases based on quite small numbers of students, and could possibly be quite unstable from one year to the next. This could lead to the highly undesirable phenomenon of "shifting targets" in a program of several years duration.
The worst-case scenario is the random selection of program beneficiaries. This would be considerably less effective than even "broad stroke" geographical targeting if performance is judged by the P2 measure, although the relative advantage of "broad stroke" geographic targeting is less apparent when effect is judged by the P1 measure. We have not attempted to quantify the potential effect of mixed strategies, such as limited geographic targeting plus household screening using a proxy indicator. Such strategies might combine administrative ease (and manageable budgets) with acceptable effect. In a program context, it would be essential to incorporate into the analysis information on the administrative costs of operating over dispersed areas and of applying the screening test.
The comparison of different targeting options for nutrition programs is
possible in Honduras because of the existence of a national census of
the nutritional status of first-graders. Strictly speaking, the
results of this analysis are applicable only to interventions focused
on first-graders because we cannot be sure that the nutritional
status of younger children in Honduras is similarly distributed among
local communities, municipalities and departments. It is the case,
however, that sample surveys of the nutritional status of children <5
y old in Honduras have consistently found regional patterns that match
the departmental rankings evident in the school height census [see,
for example, Government of Honduras (1997a)
]. Data
presented by Parillón and co-workers (1988)
indicate a rank correlation of 0.75 between school height census and
nutrition survey estimates of the prevalence of malnutrition in the 65
distritos of Panama, despite the fact that the two
measurements were made 2 y apart, which would presumably attenuate
the true association. The authors do not present the data necessary to
calculate the Pearson correlation coefficient, but this would usually
be higher than the rank correlation if there are any "outlier"
distritos that are particularly high (or low) on both
measures. It should be borne in mind, however, that if the correlation
between the two measures in Honduras is much <1, then the present
results will overstate the expected effect of targeting based on the
results of school height censuses on the prevalence or severity of
malnutrition in preschool children.
We chose to age-adjust the data from the Honduras school height census because of regional differences in mean age at enrollment. It could be argued, however, that the age bias works in favor of targeting the poorest schools and areas because schools with the most delayed enrollment are situated in the poorest areas, where the most malnourished children are found. This point should be considered by those intending to use school height census data for targeting; it does not substantially affect the present results, however, because there was only a 25-mo difference between the 10th and 90th centiles of the age distribution in the school height census data used. Clearly, in other countries in which school height censuses are not able to achieve such high coverage as in Honduras and/or selectivity biases are more pronounced, the usefulness of this tool would be diminished, and other sources of information might have to be explored.
In conclusion, geographic targeting has the potential to substantially enhance the effect of nutrition programs on the severity of stunting in Honduras, especially if fine-level targeting is feasible. Assuming that effect is quantified using a measure that distinguishes between gains to the severely malnourished and gains to the marginally malnourished, such as the P2 measure proposed in this paper, any kind of geographic targeting is better than none. No form of geographic targeting is able to achieve the level of effect seen with individual-level targeting, even if the indicator used does not correlate perfectly with achieved nutritional status. However, the costs of individual-/household-level screening are several orders of magnitude greater than for geographic targeting, and the administrative costs of running a geographically dispersed program are also expected to be very large. It will be important to determine whether similar results pertain in other countries with different baseline levels and distributions of childhood malnutrition.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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Manuscript received November 2, 1999. Initial review completed February 1, 2000. Revision accepted June 14, 2000.
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