Dynamic census

In the past decade, use of mobile devices has increased significantly and mobile phones are widely used by the vast majority of the population in most countries, including in low income countries. Every call or text message from a mobile phone is recorded in a Call Detail Record (CDR) by the Mobile Network Operation (MNO). The CDR has details like timestamp and cell tower location which can be used to find the approximate location of the caller. CDR’s are routinely and passively collected by MNOs for billing and network management purposes. Due to wide geographic coverage of mobile networks, CDR’s can provide population data with high resolution on space and time, and this information could help in policy making. This activity, carried out in Sri Lanka, used anonymized mobile phone data to develop dynamic demographics data on a nationwide level.

The Dynamic Census project, led by the University of Tokyo, enabled the capture of population-level data, disaggregated by gender, age category, and employment status. Statistics extracted represented the general population and provided the changes in population in gridded maps at 30-minute intervals. The footprint of people as trajectories could be observed alongside existing transport networks and buildings. This approach enhanced the ability to develop up-to-date statistics of large populations. Insights derived from the Call Detail Records (CDRs) supplemented population and housing census data with the addition of dynamic aspects of population distribution. It resulted in disaggregated population statistics in a timely manner.

This project addressed SDG 11- Sustainable cities and communities. The Dynamic Census helped extend the coverage of conventional population statistics. It facilitated the capture of data for marginalized populations, such as those residing in informal settlements and floating populations. Because the size and economic impact of such populations were not negligible, improving the understanding of their conditions is crucial for effective developmental intervention.

This method was replicable, as most of the data inputs were not country-specific. CDRs are routinely collected/accumulated by MNO for billing and exist wherever mobile networks operate. Furthermore, the structure of a CDR does not vary greatly according to countries and regions. Transport network data can be extracted from OpenStreetMap (OSM), which is an open-licensed data platform. 

This approach does not replace conventional censuses but rather complements them with respect to granularity, frequency, and coverage. Particularly for lower-income countries where official statistics and population distribution data are limited and outdated, this approach can significantly augment existing knowledge.

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