Uncorrected refractive error - a condition affecting nearly 1 billion people globally - is a potentially significant constraint to economic productivity. Despite its prevalence, limited research has explored productivity impacts from refractive error correction in low-and middle-income countries where 90% of avoidable sight loss occurs. This study estimates the effect of refractive error correction on productivity by providing glasses to 332 seasonal harvesters across 12 Guatemalan coffee operations during the 2023-2024 season. Daily harvest weights were recorded and compared to a non-intervention group without visual impairment. We used an ANCOVA model as the primary specification with alternative difference-in-differences specifications as robustness checks. A financial benefit-cost analysis assessed whether returns exceeded costs for workers and farm owners. Results show a significant average daily harvest increase of 12. 2 lbs (95% CI 3. 5-20. 8, p = 0. 004), corresponding with a 7. 9% relative productivity gain (95% CI 1. 0%-14. 8%, p = 0. 02). Providing glasses costs 29. 4 per worker, yielding returns of 10. 9 to 1 to harvesters if they make this investment directly and 2. 6 to 1 to the farm owners if they provide the glasses. Findings indicate substantial productivity gains and financial incentives for vision correction. This simple, cost-effective intervention has the potential to benefit millions in agriculture.
Everett et al. (Mon,) studied this question.