the treatment station (RTS) rewarded both the tenth and eleventh callers such that there were twice as many winners among households residing in villages assigned to RTS than among households residing villages assigned to the control SUD FM station. The script of the contest clips is presented in Section A2 of the Appendix.

As part of the encouragement design, callers received an automated feedback text message on their mobile phone within 24 hours, indicating whether they called before the countdown, were among the first nine callers, the winner, or called after the tenth caller.<sup>17</sup> The cash transfers were implemented via the service provider Wizall. We opted for the call-in contest rather than a lottery as in Berg and Zia (2017) because, according to the study’s formative research, households in the study area are frequently invited to marketing campaigns that follow a lottery format but typically do not have experience of people winning prizes through these campaigns. Hence, trust in marketing campaigns is generally low. By naming it a call-in contest, we aimed to avoid an association with other marketing campaigns. We aimed to increase trust in the process by giving households both (the feeling of) slight control over the odds of winning a price and comprehensive feedback on how close they were to winning on each attempt.

The evaluation design of radio broadcasts addresses three common concerns when evaluating mass media broadcasts. First, participants may be more likely to listen to the radio than if they had not been incentivized. We note that radio listenership in Senegal is currently very high.<sup>18</sup> As such, we expect the incentive to be more likely to induce people to listen to a particular radio station rather than inducing to listen to radio at all. Second, when listening to the radio, participants might pay closer attention to the radio messages than they would do otherwise. We do not base rewards on the remembering of content from the show, and the radio component of the campaign occurs during advertising breaks where the contest was not aired. In doing so, we arguably mitigate the concern that people are artificially induced to listen more intently to the materials than they would normally do, an advantage over the Berg and Zia (2017) study. Third, self-selection issues may arise from inherent differences to the radio stations. However, the stations were selected based on listenership, information about the call-in contest, including the timing of the contests (morning and evening throughout May 2016) and the dial-in number of the respective radio station.

> 17 Only phone numbers provided in the baseline survey were able to establish a connection with the dial-in number to avoid unnecessary traffic on the line and restrict cash transfers to the study population. In the rare event of households participating in the call-in contest of the wrong radio channel, they received a text message with the information about their ineligibility for the cash price under this dial-in number together with the dialin number of the right radio station.

> 18 Our baseline data convey that more than 69 percent of the population listened to the radio during the previous day.

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