In the context of this study, only about one in four households purchased a test, regardless of the offer type, despite the low—and subsidized—sale price and widespread awareness about the arsenic problem, and despite little prior awareness about the safety status of individual wells. This is consistent with a growing literature that documents low demand for health-protecting technologies in developing countries for a variety of such products, ranging from insecticide-treated nets (Cohen and Dupas 2010, Dupas 2014, Tarozzi et al. 2009, Tarozzi et al. 2014), to de-worming drugs (Kremer and Miguel 2007) and water-disinfectant (Ashraf et al. 2010). However, while the offer type barely affected demand, it did affect how households responded to the information. Intent-to-Treat estimates ( _not_ conditional on purchase) show that while standard individual sales led 3.7% of households to switch water source, the fraction was 4.3% with group sales (14% higher, 95% C.I. [ _−_ 0 _._ 0137 _,_ 0 _._ 0339], p-value 0.404) and 6.4% (75% higher, 95% C.I. [0 _._ 003 _,_ 0 _._ 072], p-value 0.031) when metal plates were attached to the well spout in case of purchase, although the difference is only statistically significant in the latter case. In addition, the estimates show very substantial differences between arms in the response of households who receive ‘bad news’ about the safety of their well water. Among households informed that their well is high in arsenic, switching rates almost doubled from 30 to 56% with group sales relative to standard individual sales (95% confidence interval of the difference adjusted for baseline covariates is [0 _._ 011 _,_ 0 _._ 362]). Switching rates also more than doubled when metal plates were attached to the pump head (from 30 to 72%, 95% C.I. of adjusted difference [0 _._ 188 _,_ 0 _._ 609]).

This work complements the literature on the demand for health-protecting technologies by looking at demand for health-related _information_ that can be exploited by households to reduce risk. The focus here is on the offer of information that is specific to the buyer (the test measures arsenic contamination in the water from a specific well), in contrast to general information (for instance, on the likelihood of arsenic contamination, or the health risks associated with unsafe water). While this article studies demand for information on environmental factors, earlier work has considered the demand for information on health status, see in particular Cohen et al. (2015), Bai et al. (2017), Thornton (2008), and Gong (2015). These studies suggest that even among households willing to pay for information, behavioral responses may not be optimal from a public health perspective, so that it is important to study whether the mode of delivery of information can help achieving desirable policy objectives.

This article is related to Barnwal et al. (2017) who estimate a very steep demand curve for arsenic tests in Bihar, India, another location with a groundwater arsenic problem. This study found that uptake was 25% at a price of INR40 (about BDT49), which is about the same as what this study estimates at a very similar price of BDT45. Unlike Barnwal et al. (2017), this study does not analyze how demand changes with price, but it examines the role of non-price factors on demand and behavioral responses to information. The results show that demand was not sensitive to the introduction of informal agreements or the use of placards, but conditional on demand, these nudges led to large and significant increases in switching among users of unsafe wells relative to simpler, private sales.

The paper proceeds as follows. The next section provides additional background information on the extent of the arsenic problem in the study area and describe the experimental design. Section 3 de5