This is the 14th in this year’s series of posts by PhD students on the job market.
Child nutrition improved across West Africa from 1990 to 2018. Ghana, Senegal, and Côte d’Ivoire reduced stunting to about 17 to 21 percent. Southern Nigeria followed the same path. Northern Nigeria did not.
A child born in northern Nigeria faces stunting rates more than twice as high as a child in the South. Northern rates stayed near 50 percent while the South fell toward 21 percent. The gap in 1999 was 18 percentage points. After 2000 it began to widen. By 2018, the North had levels close to the poorest parts of the Sahel.
This split is striking. Both regions had the same federal health programs, the same vaccination drives, and the same macro shocks. Yet their child health outcomes moved in opposite directions.
What changed in 2000?
The answer to this peculiar health crisis lies in an institutional reform that transformed criminal justice across 12 northern states. In January 2000, Zamfara State adopted Sharia Penal Codes (SPC), transferring criminal jurisdiction from secular to Islamic courts. Within months, 11 other states followed. The reform codified stringent child protection regulations, classifying abandonment and neglect as criminal offenses, with sentences ranging from corporal punishment to incarceration for several years. It also formalized filial obligations requiring adult sons, but not daughters, to provide old-age parental support.
Implementation varied by state. Eight states enforced both incarceration and corporal punishment with robust oversight through the Hisbah police, an Islamic law enforcement institution. Four states applied more limited sanctions with weaker enforcement mechanisms. This variation created a natural experiment to understand how institutional quality shapes reform outcomes.
My job market paper reveals how enforcement intensity determined who benefited and who suffered, with profound implications for child health across religious lines.
The evidence
I use six rounds of Nigeria's DHS from 1990 to 2018, covering roughly 60,000 children under five, with detailed anthropometric measurements, maternal characteristics, healthcare utilization, and fertility data. I employ a difference-in-differences design comparing children born before and after 2000 in reform versus control states, with extensive robustness checks including synthetic control methods, border discontinuity designs, and analysis of spatial variation in mosque density.
The reform reduced child health significantly. Effects ranged from 0.23 to 0.29 standard deviations across three WHO measures: height-for-age, weight-for-height, and weight-for-age Z-scores. Height-for-age showed the largest effects, capturing chronic undernutrition rather than acute nutritional shocks. This points to disrupted long-term health service utilization rather than immediate food shortages.
Non-Muslim minorities bore the heaviest burden. They experienced height-for-age reductions of 0.76 standard deviations and weight-for-age reductions of 0.44 standard deviations, approximately three times the Muslim impact. This moved the average non-Muslim child from -1.0 SD to -1.77 SD, pushing them from borderline normal nutritional status toward moderate stunting. Muslims showed no significant height-for-age changes and only moderate weight-for-height reductions of 0.18 standard deviations.
When institutions protect (or fail)
Child protection laws harmed children in some states and protected them in others. The difference was not the law. It was enforcement. Figure 1 tells this story.
Weak enforcement created a two-tier system. In low-penalty states, non-Muslim children bore catastrophic losses. Height-for-age collapsed by 1.45 standard deviations, pushing children from borderline normal (-1.0 SD) into severe stunting territory (-2.45 SD). Weight-for-age dropped 1.23 standard deviations. Muslim children in the same states fared significantly better, declining only 0.52 standard deviations in height-for-age.
Figure 1. Reform enforcement heterogeneity
Strong enforcement eliminated the religious divide. Results from high-penalty states tell a different story. Non-Muslims experienced manageable declines: 0.47 standard deviations in height-for-age, staying within mild stunting range. Muslims showed minimal effects of 0.14 standard deviations. Most importantly, the religious gap that defined low-penalty states does not appear to be present for children in high-penalty states. Where oversight was strong, religious identity did not contribute to child health.
The high-low comparison proves institutions matter more than identity. Direct comparison between high-penalty and low-penalty states shows 0.61 standard deviation improvement in height-for-age under strong enforcement. This protection applied equally to Muslims and non-Muslims. No religious difference emerged. The pattern is clear from the above discussion: weak enforcement amplified religious disparities while strong enforcement erased them.
A puzzle with two answers
Why would child protection laws harm children? The answer differs by religious group.
For Muslims: Strategic Fertility Under Legal Pressure
The reform created competing pressures. Penalties raised the cost of child neglect, encouraging health investment. But formalized filial obligations exclusive to sons created pressure to secure male children for old-age support.
This triggered strategic fertility responses that varied by household composition. Muslim households with a male firstborn experienced a differential fertility reduction of 0.35 births due to the reform. And this translated to increased child investment (immunization rates) by 10.4 percentage points. Figure 2 shows these households achieved differential health gains between 0.19 and 0.33 standard deviations.
Figure 2. Son preference and child health investment
Households without sons increased fertility by 0.67 births to secure a male heir, which reduced the resources available for each child. This pattern is consistent with earlier evidence showing higher fertility after the Sharia Penal Codes reform (Godefroy, 2019; Alfano, 2022). These opposing behaviors, with greater investment among families with sons and higher fertility among those without, offset one another and explain the mixed overall effects among Muslims.
For Non-Muslims: Discrimination Varies with Enforcement
Non-Muslim minorities fell outside the reform's legal framework but not outside its reach. Outcomes depended entirely on enforcement capacity.
High-penalty states with strong institutional oversight constrain discriminatory practices through systematic monitoring. Officials have less discretion to apply reforms selectively. Low-penalty states with weak enforcement allow officials greater latitude to restrict minority access to healthcare and essential services.
Results from the Afrobarometer survey confirm this hypothesis. I find non-Muslims in reform states reported feeling less fairly treated by government, down 12.8 percentage points. Within reform states, non-Muslims in high-penalty areas reported fair treatment 46.6 percentage points higher than those in low-penalty states. This fed directly into healthcare access: they were 17.4 percentage points more likely to seek antenatal care and 20.8 percentage points more likely to immunize children.
Comparisons to control states sharpen this narrative. Non-Muslims in low-penalty states were 23.7 percentage points less likely to seek antenatal care and 38 percentage points less likely to immunize children than non-Muslims in control states. Those in high-penalty states were 39.1 percentage points more likely to report fair treatment than non-Muslims in control states.
Two lessons for Policy
First, enforcement design matters as much as policy content. The same legal framework produced opposite outcomes depending on institutional strength. This challenges conventional policy evaluation that focuses on whether reforms exist rather than how they function in practice.
Second, targeted policies create unintended spillovers onto non-targeted groups. A reform designed to strengthen Muslim family structures imposed the largest health costs on non-Muslim minorities who fell outside its legal framework but not outside its reach. This pattern echoes findings from other contexts where selective policies generate uneven welfare impacts (Burgress et al., 2015).
Hardi Ahmed is a PhD candidate at the University of Alicante. You can find his personal webpage here.
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