significant change in the sex-composition of first births by socio-economic group after ultrasound technology became available.

Exogeneity of firstborn sex has also been previously defended (Das Gupta and Bhat (1997), Visaria (2005), Bhalotra and Cochrane (2010)). It also lines up with recent survey data that suggest that parents do not always prefer having a son over a daughter. Jayachandran (2016) finds that although the vast majority of families want to have a son if they can only have one child, at a family size of two they prefer having one daughter and one son over having two sons. As desired and actual fertility in India are well above one (Table A.5), it is reasonable to assume that parents are not averse to having one girl, despite a strong desire for at least one boy. In our sample, on average, desired fertility is 2.7; the desired number of sons and daughters are 1.38 and 1.01, respectively.

**Pre-trends not different by firstborn sex.** In order to test for a significant difference in trends in under-5 mortality and health investments for firstborn-boy and firstborn-girl families in the pre-ultrasound period, we restrict the sample to the pre-ultrasound period, 1973-1984, and regress the outcomes of interest on the full set of interactions between indicators for firstborn girl ( _Gj_ ), female birth ( _Fi_ ), and year of birth, with and without fixed effects for birth order and state, and examine the coefficients of the triple-interactions. The coefficients from these regressions are presented in Figure 4 which demonstrates no significant divergence between EFM, immunization, and breastfeeding in firstborn-boy and firstborn-girl families for pre-ultrasound cohorts for children of parity greater than one. The same is true for pre-trends estimated separately for the sub-samples of boys and girls (see Figure A.1).

**Firstborn sex predicts sex-selection at higher parities.** Previous studies, namely Bhalotra and Cochrane (2010) and Rosenblum (2013), have established that parents randomly exposed to a “firstborn-girl treatment” are more likely to practice sex-selection at higher-parity births, consistent with a documented desire for at least one son. Figure 3 clearly depicts this pattern: after ultrasound technology became available, second, third, and fourth births became increasingly male but _only_ for families without a son.<sup>25</sup> So, the interaction with first child’s sex captures the differential incentives to sex-select among otherwise similar families.

# **4.1 Unconditional Trends in Outcomes**

Our main findings are evident in the raw data. Table 1 shows that in the pre-ultrasound era, 1973-1984, averaging across families with a firstborn girl, girls were 2.87 p.p. more likely than boys to suffer under-5 mortality. After 1985, following introduction of ultrasound, the gender gap in mortality declined for this group, to 1.59 p.p. during 1985-1994 and to 1.09 p.p. during 1995-2005. In comparison, EFM in families with a firstborn son was close to zero pre-ultrasound (indeed, it was negative at -0.08, vastly different from 2.87 p.p.). Moreover, there is no evidence that postultrasound mortality reductions favored girls in this group.

> 25The graphs look similar if we compare the proportion of females among third and fourth births by sex instead.

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