Using a combination of the CDR aggregates described here, we can generate a range of mobility indicators which are useful for planning the COVID-19 response. Analysis is required to produce these indicators which may comprise data cleaning, aggregation of data across time periods, or rescaling to account for biases within data.

Note that all aggregates need to be computed for a period of at least four weeks before interventions were introduced, or before the initial COVID-19 cases were announced in the country. This is to obtain indicators about routine baseline mobility, against which the post-intervention indicators can be compared. Aggregates should then be produced continuously throughout the epidemic, with a frequency that meets the needs of the data consumers.

Indicators we suggest can be regrouped in the following categories, based on the main CDR aggregates they are derived from:

• Subscriber presence: how visited places are over time and regularity of pattern

• Home locations: changes to the population distribution

• Crowdedness: how busy and how often busy places are

• Population mixing: how many different people visit the same place over time

• Intra-regional travel: quantity of movement within a region

• Inter-regional travel: quantity of movement across regions for all pairs of regions and quantity of movement from home

• Locations of interest: hotspots, main travelled routes and secluded areas

• Sample size / data quality indicators