Behavioral Response to an Anti Malaria Spraying Campaign, with Evidence from Eritrea

It is sometimes argued that introducing Indoor Residual Spray (IRS) in areas with high coverage of mosquito bed nets may discourage net ownership and use, which would hinder Malaria eradication rather than promote it. We analyze new data from a Randomized Control Trial conducted in Eritrea in 2009, and we show that this does not happen in practice. IRS actually induced households to acquire more nets and even led to increased net use among certain demographic groups. IRS was further not associated to any perverse behavioral response. We explore two arguments that can explain this. The IRS campaign may have conveyed information about the importance of preventing Malaria and about how to do so, and people adjusted their behavior accordingly. Alternatively, people may perceive bed nets and spray as complements, even though they are substitutes. Further research is needed to disentangle these two effects.