Mobile phones have spread throughout developing countries, largely without complementary information services that allow users to search the mobile phone network. This paper develops a model that predicts both productive and distributive benefits from information services that lower the cost of communication between households and enterprises.

To test hypotheses implied by the model, the authors conducted a set of paired RCTs in central Tanzania, centered on the production and distribution of a telephone directory relevant to agricultural households. The projects randomized enterprises into the directory during a trial period, and randomized household access to the directory at the village level.

The directory had substantial impacts on both sides. Enterprises saw large increases in the volume of calls and the use of mobile money. Directory recipients increased search activities and the use of mobile phones for business purposes. There is suggestive evidence of improved farming outcomes for recipients. Survey-based and incentivized measures of willingness-to-pay to be listed (for enterprises) or to receive a directory (for potential recipients) make it possible to estimate the optimal level of directory subsidization.