defecation rates. Pakistan’s results largely mirror those for Bangladesh and Nepal, two countries which observed larger gains in average HAZ over somewhat shorter periods than Pakistan. Notwithstanding, as noted in the study, the decomposition results should be cautiously interpreted. The results are not causal; factors that have shown relatively little gain in levels would have contributed little to the gain in average HAZ, although these factors may be fundamentally important. Further, other factors that may have substantially contributed to the gain in average HAZ were omitted from the analysis because they were not measured (in the same way) across the countries and in the DHS rounds.

Headey, Hoddinott, and Park also find that the estimated effects (or returns) of the factors in the HAZ regressions remain mostly unchanged over time in Pakistan—similar to the result they find for other South Asian countries. This finding suggests that the contributions of various factors to the gain in average HAZ are due to gains in the levels of the factors, and not to gains in the returns to the factors.

# **Box 2. Substantial household economic gains but little to no child nutrition gains?**

World Bank (2016a) finds that the national household consumption poverty rate declined substantially over the period from 2001–02 to 2013–14. Consistent with the decline in poverty, poorer households experienced a large increase in asset ownership. Poorer households also spent less on cereals, and more on other (costlier) foods, leading to higher real spending per calorie, but also greater household dietary diversity. Nevertheless, as Figure 4, Panel A shows, undernutrition rates did not improve over the 2000s and early 2010s.

Why has the large decline in household poverty not been accompanied by a large gain in child nutrition status? The question is perplexing because studies that examine the cross-sectional association between household economic status and child nutrition status based on household survey data tend to find a significant, large positive association, even after controlling for other factors (for example, see Di Cesare et al. 2015; Haddad et al. 2003; Mahmood 2001). Indeed, household-level factors that some studies control for—such as the level and composition of food consumption, use of health services, access to improved water and sanitation facilities—may function as some of the pathways through which household economic status influences child nutrition status. Illustrative of the important role of household economic status, based on 2011 NNS data, the World Bank provincial nutrition status notes find that children in the bottom two wealth quintiles are 38% to 240% more likely to be stunted than children in the top wealth quintile in province-specific regressions. Based on DHS data, Headey, Hoddinott, and Park (2016) find that the gain in household economic status accounts for 27% of the gain in average HAZ predicted by changes between 1990–91 and 2012–13 in allthe factors that they examine. Arif et al. (2014) is an exception. Based on the rural household panel subsample of the PPHS, they find that the effects of instrumented lagged household consumption spending on HAZ, WHZ, and WAZ are insignificant.

This puzzling pattern is also found in relation to caloric consumption in Pakistan. World Bank (2016a) and other studies, looking at a single national household survey round in a given year, find that household caloric consumption has a strong, positive association with household economic status. Looking across national household survey rounds over time, however, they find that average household caloric consumption declines, while average household economic status improves.

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