areas in Pakistan at the top and bottom ends of the nutrition-status range; and what are the factors behind declining caloric consumption, but rising real spending, in rural households?

More, rigorous empirical evaluations of nutrition-related interventions are needed, composed of components that evaluate implementation performance, impact, and cost-effectiveness. The impact-evaluation component would be more informative if it examines short- and long-term effects, the variation in effects across different subpopulations, effects on indicators that reflect potential pathways behind outcomes, and effects on multiple health and nutrition outcomes. A good-practice model is the experimental evaluation of the effects of early childhood stimulation and enhanced nutrition interventions, discussed by Yousafzai et al. (2016), Yousafzai et al. (2014), and Gowani et al. (2014).

Empirical studies on the determinants of nutrition status based on large-scale, representative household surveys may be more informative if the surveys collect data on:

- (1) additional/refined dimensions related to breastfeeding, child feeding, WASH, and environmental pollutants;

- (2) health and nutrition promoting and damaging behaviors of mothers and children;

- (3) traditional beliefs and behaviors that qualitative studies suggest are key determinants of nutrition status;

- (4) food allocation among members within the household;

- (5) the uptake of main public, NGO, and private nutrition-related interventions; and

- (6) economic, social, and environmental shocks experienced by the household, including conflict, violence, and insecurity.

The collection of large-scale or multi-site longitudinal survey data—tracking girls from adolescence into adulthood, and their children from birth onward—may also make research on determinants more insightful. Studies by Fikree and Berendes (1994) and Fikree, Rahbar, and Berendes (2000), which tracked a sample of women through their pregnancies and, later, their children through early childhood, are a partial example. Large-scale measurement of the quality of food consumed and health services received by mothers and children could prove useful, although quality indicators are more difficult to collect. More large-scale data collection and research are needed on micronutrient deficiencies in children, and on the health and nutrition status of adolescent girls and women. Repeated surveys that have extensive health, nutrition, and consumption expenditure modules (i.e., a marriage between the DHS and World Bank Living Standards Measurement Surveys) would be useful for examining whether the trends in household caloric consumption and child nutrition status in Pakistan are related, and, if so, the nature of the relationship, including whether the trends are jointly explained by factors that have not improved, despite the broad gains in household economic status documented for the country.

Credible, regular, and representative data on maternal and child nutrition outcomes are vital for evidence-based policymaking. The large-scale representative household surveys regularly administered in Pakistan represent a major effort and contribution. However, measures are needed to minimize the rates of survey nonresponse and missing or invalid child anthropometry data, based on diagnostic research into the factors that contribute to missing or invalid data. Absent such measures, nutrition statistics for Pakistan can be unreliable, making it difficult to accurately assess progress in addressing undernutrition.

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