In rural Africa, basic mobile phones help people conduct business among their existing contacts. But expanding business networks – and opportunities – remains a challenge.

New research by two Cornell faculty members and their colleague shows that introducing paper business telephone directories – similar to the Yellow Pages – in Tanzania boosted sales revenue by 104% for listed businesses and increased the number of sales and the use of mobile money. Neighboring unlisted businesses also benefited. The work published May 14 in The Economic Journal.

“When you and I use our phones in the U.S. and Europe, we’re in this enriched information and communications technology [ICT] environment where we can access contact information for most other people and businesses very easily,” said Brian Dillon, lead author and assistant professor of applied economics and policy at the Cornell SC Johnson College of Business.

That’s not the case in rural Africa, where businesses don’t usually have websites and most mobile phones don’t have search capabilities to find them anyway, Dillon said.

“We wanted to test whether or not contact information is a key bottleneck for the potential of mobile phones to support farmers and businesses, to foster new trading relationships and to have as broad benefits as possible,” he said.

Without a directory, basic business activities can be costly. A phone alone doesn’t provide access to all the traders or sellers a business owner might want to contact. If a farmer wants to find lower-cost fertilizer, for example, they need to leave their farm for a day, spend money on travel, and talk to a lot of people in a neighboring town. And the payoff is uncertain. “It’s prohibitively costly to do a lot of this,” he said.

With the support of the Institute of Rural Development Planning, Dillon, his coauthors and their team of assistants completed a census of businesses in central Tanzania and obtained permission to include their contact information in the print directory.

The first versions of the directory listed a subset of the businesses, so the team could compare the impacts on listed versus unlisted firms. To safeguard against potential negative effects, the team ensured that groups of competing businesses would either all be listed or all left out of the directory. At the conclusion of the study, they created a complete directory and distributed thousands of copies in the area.

The researchers found the directory made a big impact on listed businesses as well as their neighbors. The magnitude was “life-changing for small businesses,” Dillon said.

In addition to the 104% increase in revenue for listed firms, the number of sales increased by 47% and the use of mobile money by 31%.Unlisted neighboring firms increased text message traffic by 280%, mobile money usage by 26%, and the number of sales by 40%. Dillon attributes the increases to time and direct costs saved by being able to search for businesses and opportunities from homes, using their phones.

Dillon received a lot of positive feedback from businesses, he said. One man told him that his motorbike broke down outside of town, and, in the past, he would have had to push the bike miles to a repair shop he knew. With the directory, he found and called a nearby mechanic, who traveled to him.

Now, Dillon and his team are analyzing the effects of a digital version of the directory, accessible by mobile phones using unstructured supplementary service data, or USSD – a technology that does not require a smartphone or an app.

“We’re hoping that the evidence that we’ve generated will push more policymakers to support this kind of program and more entrepreneurs to potentially try to do this elsewhere,” he said.

Co-authors of the research are Jenny Aker, the Daniel G. Sisler Professor of Development Economics in the College of Agriculture and Life Sciences, and Joshua Blumenstock of the University of California, Berkeley.

Alison Fromme is a writer for the Cornell SC Johnson College of Business.