Rema Hanna, Esther Duflo and Michael Greenstone are the authors of a study on the long-run impact of improved cookstoves on health. The authors track households for up to 4 years after they received the stove. While they find a meaningful reduction in smoke inhalation in the first year, there is no effect over longer time horizons. They find no evidence of improvements in lung functioning or health and there is no change in fuel consumption (and presumably greenhouse gas emissions). The difference between the laboratory and field findings appears to result from households’ revealed low valuation of the stoves. Households failed to use the stoves regularly or appropriately, did not make the necessary investments to maintain them properly, and usage rates ultimately declined further over time. More broadly, this study underscores the need to test environmental and health technologies in real-world settings where behavior may temper impacts, and to test them over a long enough horizon to understand how this behavioral effect evolves over time.