Most studies find that age is associated with nutrition status.<sup>34</sup> Panel A in Figure 5 shows undernutrition rates by age groups, based on 2012–13 DHS statistics. The rate of stunting increases with age before declining somewhat, the rate of wasting declines with age, and the rate of underweight appears to be constant over age, presumably reflecting the opposite pulls of stunting and wasting.<sup>35</sup> Tracking a sample of children, Fikree, Rahbar, and Berendes (2000) examine the bivariate association between age and nutrition status, and find that the likelihoods of underweight and wasting status increase with age measured from three to 24 months, and that the likelihood of stunting status increases with age from three to 18 months, and then drops at 24 months.

With respect to the effect of gender, the 2012–13 DHS finds poorer nutrition status for boys: specifically, female and male stunting rates of 42% and 48%, female and male wasting rates of 10% and 12%, and female and male underweight rates of 27% and 33%. These levels are consistent with the general finding that boys naturally have poorer health status than girls, as indicated by illness, disability, and death.<sup>36</sup> They also mirror the general pattern of stunting rates across genders in other developing countries (IFPRI 2016).

The preference for sons is generally viewed as strong in Pakistan. Bongaarts (2013) ranks Pakistan as having the second-highest desired sex ratio for boys, out of a total of 61 countries. Despite this, several studies for the country find that the effect of gender on nutrition status is insignificant.<sup>37</sup> As exceptions, Arif et al. (2014), Baig-Ansari et al. (2006), and Hazarika (2000) find significantly poorer nutrition status for boys.

The gender gap in nutrition status may be small and insignificant because of preferential treatment of boys that offsets their natural health disadvantage.<sup>38</sup> The direction of the gender gap is also consistent with the hypothesis that the preferential treatment of boys may worsen their nutrition status if parents invest more in boys than girls but unknowingly adhere to incorrect traditional beliefs and practices with respect to child health and nutrition. For example, Fikree et al. (2005) and Kulsoom and Saeed (1997) spotlight the customary practice of giving a child prelacteal or supplemental feeds, such as honey and tea, and Baig-Ansari et al. (2006) find that the intake of tea by the child is positively associated with stunting status based on a bivariate test. Notwithstanding,

> 34 See World Bank provincial nutrition status notes; Fazal et al. (2013); Baig-Ansari et al. (2006); Mahmood (2001); Hazarika (2000); Ibrahim (1999); Alderman and Garcia (1994).

> 35 This pattern is corroborated by 2011 NNS statistics.

> 36 The medical literature suggests a genetic disadvantage for boys. Boys are at greater risk for premature birth, have less well-developed lungs, and thus are more likely to die from perinatal causes than girls. Boys have weaker immune systems and higher rates of mortality and morbidity from viral, bacterial, and parasitic infections in infancy and childhood than girls. Their greater propensity for physical activity, aggression, and risktaking also makes boys more likely to experience death and disability due to accidents and violence (Muenchhoff and Goulder 2014; Simchen et al. 2014; United Nations 1998).

> 37 See Headey, Hoddinott, and Park (2016); Ullah et al. (2014); Haddad et al. (2003); Mahmood (2001); Ibrahim (1999); Alderman and Garcia (1994). The World Bank provincial nutrition status notes do not find gender is associated with stunting status, in either a bivariate or a multivariate test depending on the province.

> 38 The 2012–13 DHS finds that 70%, 67%, and 56% of boys were treated for ARI symptoms, fever, and diarrhea respectively, compared to slightly lower rates of 68%, 64%, and 53% for girls. Alderman and Gertler (1997) find that poorer households seek care more often and are more likely to use higher-quality providers (proxied by private doctors) for boys than girls. Hazarika (2000) finds that boys are more likely to be immunized than girls. Hafeez and Quinatana-Domeque (forthcoming) find that mothers breastfeed daughters less (especially if there are no older sons), presumably in order to become pregnant again to conceive a son. They also find that, at ideal fertility, sons are breastfed on average 1.3 months longer than daughters.

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