In 2013, the data-driven international development company Knuper acquired call detail record (CDR) data from the telecommunications company Orange/Sonatel as part of its Data for Development Challenge. Using this data, Knuper conducted a study "determining the usability of CDRs to improve measurements of illiteracy in developing countries." The researchers expanded on [their methodology](https://rss.onlinelibrary.wiley.com/doi/full/10.1111/rssa.12305) in a paper subsequently published. In it, they describe how they used anonymized CDRs covering the year 2013. The dataset "is based on more than 9 million unique mobile phone numbers and represents a market share of around 60%. In particular, we had access to the tower‐to‐tower traffic of all 1666 mobile phone towers in Senegal."