About 10% of primary school students in developing countries have poor vision, but very few of them wear glasses. Almost no research examines the impact of poor vision on school performance, and simple OLS estimates could be biased because studying harder may adversely affects one's vision. This paper presents results from a randomized trial in Western China that offered free eyeglasses to rural primary school students. Our preferred estimates, which exclude township pairs for which students in the control township were mistakenly provided eyeglasses, indicate that wearing eyeglasses for one academic year increased the average test scores of students with poor vision by 0.16 to 0.22 standard deviations, equivalent to 0.3 to 0.5 additional years of schooling. These estimates are averages across the two counties where the intervention was conducted. We also find that the benefits are greater for under-performing students. A simple cost-benefit analysis suggests very high economic returns to wearing eyeglasses, raising the question of why such investments are not made by most families. We find that girls are more likely to refuse free eyeglasses, and that parental lack of awareness of vision problems, mothers' education, and economic factors (expenditures per capita and price) significantly affect whether children wear eyeglasses in the absence of the intervention.
Bibliographical noteFunding Information:
Data collection for the Gansu Survey of Children and Families was supported by grants from The Spencer Foundation Small and Major Grants Programs (wave 1), by NIH Grants 1R01TW005930-01 and 5R01TW005930-02 (wave 2), and by a grant from the World Bank (wave 2). Travel was supported by the Center for International Food and Agricultural Policy at the University of Minnesota. We would like to thank numerous seminar participants, as well as the co-editor and two anonymous reviewers, for very helpful comments on earlier drafts of this paper.
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- Heterogenous effects
- Randomized control trial
- Test scores