own radios; television ownership in this sample is uncorrelated with access to good radio signals. Newspapers also have little penetration. The largest has a circulation of 7,000, and that almost entirely in the capital city of Cotonou. Interviews with radio station staff indicate, however, that their news reports about Benin are often prepared based on reports from the Cotonou newspapers.

# **4. Identification—The “natural experiment” in northern Benin**

As in all work on media effects, the analysis here confronts the possibility that unobserved factors influence both media access and outcomes of interest, such as whether households have received bed nets from the government and whether they have paid for those nets or received them for free. The radio market in northern Benin allows us to use a novel strategy to control for these factors. In particular, many small radio stations with limited signal strength dominate the media market, each carrying similar programming that is likely to influence household demand for bed nets. Because the stations are small, dispersed and numerous, villages that are close to each other and not separated by any remarkable topographical features can nevertheless exhibit significant differences in access. Short distances and small changes in elevation are enough to degrade the signal received by some of them. These differences are unlikely to affect bed net distribution except through their influence on radio access.

In contrast, previous research has relied on geological features that obstruct broadcasts from one or a few large stations (Strömberg, 2004; Olken, 2009; and Yanagizawa, 2009). Researchers argue that these topographical features exogenously distinguish areas with more or less radio access. Most debate centers on the exclusion assumption, that these features have no direct effect on outcomes of interest. To the extent that topographical differences between communities with more and less access are significant, the exclusion assumption is more controversial. For example, geological obstacles that leave communities with less radio access to a large station might also render them significantly more isolated in all respects compared to communities with more radio access. The effects of radio access are then entangled with those of remoteness. Issues of external validity may also be more pronounced, since the effects of media access on remote jurisdictions may not be the same as in the rest of the population.

The topographical features that yield variation in access to radio signals across villages in our sample are exogenous. However, it is possible that the location of community radio stations is not and is related to unobserved characteristics of the villages that receive them. The histories of individual radio stations, our purposive selection of the village sample and the use of commune fixed effects substantially mitigate these concerns.

Most of the small community radio stations were established through the support of donors and governments, who cared about reaching remote and rural areas but were otherwise indifferent to radio location. By themselves, these selection criteria would be ideal for our purposes. However, donors needed local partners to establish the stations. Idiosyncratic conditions within communes affected which communes yielded such partners. Ahokpossi (2009) argues that potential radio entrants in Benin viewed the commune as their relevant market and took commune-specific characteristics into account in deciding whether they would locate. Commune-specific characteristics, related to economic conditions and political struggles within a commune, therefore ultimately affected where radios were established Gratz (1999) details the history of one of these community radios, Radio Tanguieta located in Tanguieta commune in Atacora department. Local politicians controlled the community radio and Gratz reports concerns about embezzlement and over-spending on salaries of numerous radio 12