For the analysis, the number of households is reduced slightly to 13,732 due to missing values in some of the key variables, which is equivalent to 4.35% of the sample (6.63% for individuals aged 15-64).

# Mobile Broadband Coverage Data

Nigeria is the largest mobile market in Africa. At the end of 2019, there were more than 170 million mobile connections (60% of which used 3G or 4G mobile broadband technologies) and the country accounted for around one in six mobile subscriptions on the continent.<sup>8</sup> Figure 1 shows how the adoption of 2G and 3G/4G technology evolved in Nigeria between 2010-2016.

In this study, we look at mobile broadband network coverage (or availability). Coverage is distinct from usage (or access), which is when an individual has a SIM card that can be used in a mobile phone to access the internet. We look at coverage because it is not determined at the household-level and because coverage captures not only the direct impacts of individuals accessing the internet but also spillover effects. The latter includes, for example: internet users sharing information with non-users and non-users benefitting from lower market prices; job creation and productivity gains among domestic firms due to more technology use and access to international markets; or more financial capital accumulation and utilization due to increased use of digital payment platforms and mobile banking.

Mobile networks can be conceptually divided in two components. The first is the Core Network that ensures the intelligence of the network, such as switching user calls or routing user data to and from the internet. The second is the Radio Access Network, which is the collection of relay sites (i.e. towers hosting base stations and radio equipment) that connects the User Terminal (e.g. mobile phones) to the core of the network. Relay sites communicate with mobile phones in their vicinity using electromagnetic signals. The quality and availability of this communication link can be affected by several factors such as distance between the relay site and the mobile phone or the presence of obstacles (e.g. hills or buildings). A geographical area is considered _covered_ when the signal of any relay site is strong enough for mobile phones in that area to establish a usable connection link with that relay site. The aggregated coverage of a mobile network is calculated by adding up the coverage of all the relay sites in its Radio Access Network.

To produce the aggregate coverage data for Nigeria, first we collected network infrastructure data directly from three of the largest four MNOs in Nigeria.<sup>9</sup> For each individual relay site we collected

> 8 Source: GSMA Intelligence. A mobile connection is a unique SIM card (or phone number, where SIM cards are not used) that has been registered on a mobile network. Connections differ from subscribers as a unique subscriber can have multiple connections.

> 9 During the period of our analysis, the average combined market share for the three operators that we collected data for was around 75% and one of them had the highest 3G coverage in the market, with 70% of the population covered. While we were unable to collect primary data for the fourth MNO (MNO-4), we collected secondary data on the coverage of MNO-4 in 2015 and 2016 and overlapped this with our coverage data set for the other operators. We did not find any locations that were covered only by MNO-4. To test if MNO-4 could have deployed in those overlapping locations before the other three MNOs, we compared the coverage of MNO-4 with the coverage of the other operators in 2012. This highlighted nine enumeration areas (less than 1%) from the GHS data set that were covered only by MNO-4. This is also likely to be an overestimate as MNO-4 will have had lower coverage in 2012.  These tests therefore give us confidence that the lack of data for MNO-4 has a small effect, if any, on the accuracy of our coverage data set.

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