Background
The Chinese government mandated that all salt be fortified with iodine in October 1994 as part of a nationwide campaign to combat illnesses caused by iodine deficiency. Simultaneously, the government began conducting biannual province-based assessments of household salt iodine content and consumption, as well as student urine iodine concentrations. The program’s implementation led to a precipitous decline in the number of youngsters affected by goiter.
Deng & Lindeboom (2022) investigate the potential impact of this approach on the intelligence and educational performance of children who were exposed to iodine deficiency in utero. The study primarily examines how a nationwide salt iodization program in China has affected the minds of school-aged youngsters. The authors focus on how gender preferences contribute to this phenomenon.
Research Questions
- How did the implementation of the salt iodization program affect the cognitive abilities and educational outcomes of children who experienced iodine deficiency during prenatal development?
- How does parental investment differ based on the gender of the child and their starting resources, as represented by newborn weight?
- To what extent does the salt iodization program mitigate iodine deficiency’s harmful impacts on mental health, especially in girls with fewer resources at the start?
Analysis
The 1995 National Iodine Survey on goiter rates among pupils provides the baseline, pre-policy regional distribution of goiter prevalence before the introduction of the salt iodization program. In each province, 30 counties (clusters) were chosen at random from a list of counties based on their population. A random school was chosen from each county. The survey’s index sample consisted of kids between the ages of 8 and 10 at the time. Forty kids were picked at random from the list of enrollees for each cluster. The thyroid size was palpated in all of the kids as well.
The China Family Panel Studies (CFPS) provided detailed information for this analysis. The Social Science Survey Institute at Peking University conducts the CFPS, a massive, nationally representative panel survey. Before 2017, three surveys were released. A total of 14,798 families, including 33,600 adults and 8990 children, were randomly chosen for the CFPS baseline wave. The baseline survey has both a numerical and conversational component. Birth details, including date, location, and whether a person was born in a rural area, are included in the data. The focus of the scholars is narrowed to 81% of the population that was born in rural regions.
Both years of education (hence referred to as “schooling”) and a test score are used as outcome variables in the regression analyses conducted by the experts. The CFPS team developed tests in both mathematics and language to determine test scores. All pupils, regardless of their chronological ages, were given both exams. The arithmetic exam consists of 24 questions and is designed to assess both elementary and high school math skills. Each question was worth one point, and the questions were ordered from easiest to most difficult. The same applies to the oral exam, which consists of 34 standard Chinese characters. Each character is worth one point, and the characters are ranked by how challenging they are to draw.
Both the arithmetic and language tests were passed with total scores of 24 and 34, respectively. The first principal component of a principal components analysis (PCA) of the mathematics and verbal tests is used to create our primary cognitive measure (Test Score). This one variable accounts for 75% of the difference between the two assessments. Gender and parental education are two of the most fundamental socio-demographic indicators included in the sample.
The study’s results should be seen as supporting evidence for the relationship between parental investment responses and a child’s starting capital. The writers use the newborn’s weight as a surrogate for the child’s starting resources. The CFPS uses the z-score of three variables to measure parental investment: the number of times a parent reads to their child, the number of times a parent purchases books for their child, and the number of times a parent takes their child on a trip.
The three questions are nearly identical to those used in the past. Deng and Lindeboom (2022) graph the distribution of newborn weight by quartile versus the stock market index. Investment index regression findings on birth weight, gender, and the interaction between birth weight and gender are presented. It was revealed that parents make investments in their children that are positively correlated with the child’s birth weight.
The significant positive difference between boys and girls indicates that, on average, parents spend more on their sons than on their daughters. The interaction term’s negative sign indicates that the slope is negligible and significantly smaller for males. These results are consistent with other studies that have used twin data to examine the mutually reinforcing and compensatory effects of health and education spending in the wake of a health shock. Research has shown that parents facing financial difficulties often compensate by investing more in their children’s health and education.
The existing data supports the argument made by Deng & Lindeboom (2022) regarding parental investments in their children. Crucially, it reveals a spending preference for sons over daughters, regardless of the parents’ initial financial situation. When it comes to females, however, parents tend to invest more money in those who already have a lot going for them.
By iodizing salt, the government can even out iodine deficiency rates around the world. Iodine deficiency’s harmful impacts on both men’s and women’s mental health are mitigated. Less well-off girls would greatly benefit from this, suggesting that those with fewer resources at the start tend to benefit the most from the program.
Limitations
- Causality. The research is limited in its capacity to draw conclusions about cause and effect because it relies on observational data. It can indicate correlations between factors, but it cannot establish that the salt iodization program was the direct cause of the observed gains in intelligence and academic achievement.
- Generalizability. This study utilizes data from a particular iodization program in China and from rural areas. As a result, care must be taken when applying the results to other individuals or in other countries with distinct situations.
- Data Collection. Measures of parental investment may be affected by memory bias or other types of inaccuracy if they are based on data collected in hindsight. Furthermore, it may be very simplistic to use a child’s birth weight as a proxy for their initial resources and ignore other crucial elements contributing to their growth.
Recommendations
- It may be possible to draw more reliable conclusions about causation if randomized controlled trials or quasi-experimental approaches are considered. The effectiveness of the program might be better shown by including control groups and tracking results over time.
- The impacts of the salt iodization program and parental investment on child development may be better understood by broadening the scope of the research to include urban locations and a more diversified socioeconomic group.
Reference
Deng, Z., & Lindeboom, M. (2022). A bit of salt, a trace of life: Gender norms and the impact of a salt iodization program on human capital formation of school aged children. Journal of Health Economics, 83, 1–22.