Enabling analysts to produce mobility indicators from CDR aggregates

This section lists and describes, split by indicator categories, the mobility indicators that analysts can produce utilising MNOs' CDR aggregates.

For each indicator, we also list the aggregates required to produce this indicator.

Subscriber presence

Indicators based on time series of Count_subscribers aggregates

Subscriber presence - Hourly/daily presence (weekday), per region

Number of subscribers recorded in each region each hour/day, during weekdays: this describes how busy each region is during weekdays, and during each hour of weekdays

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • Count_subscribers (hour, local)

  • Count_subscribers (day, local)

  • Count_active_residents

  • Count_events

Subscriber presence - Hourly/daily presence (weekend), per region

Number of subscribers recorded in each region each hour/day, during weekends: this describes how busy each region is during weekends, and during each hour of weekends.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • Count_subscribers (hour, local)

  • Count_subscribers (day, local)

  • Count_active_residents

  • Count_events

Subscriber presence - Changes to variance of hourly/daily presence, per region

The variance in hourly/daily patterns, across different days/weeks: this provides information about the extent to which previously predictable, regular patterns have been disrupted.

Disruption duration: A further indicator may be the time it takes for presence patterns to become regular again.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • Count_subscribers (hour, local)

  • Count_subscribers (day, local)

  • Count_events

Subscriber presence - changes to day/night subscriber presence ratio, per region

Ratio of the number of subscribers recorded in each region during ‘daytime’ hours, and the number during ‘nighttime’ hours: this provides information about the number of residents (who are likely to be present during the nighttime) versus the number of non-residents (who are likely to be present during the daytime) that visit the region. It can also provide information about which regions are popular night-life spots (a high proportion of nighttime visitors).

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • Count_subscribers (hour, local)

  • Count_subscribers (day, local)

  • Count_active_residents

  • Count_events

Home locations

Indicators based on time series of Count_residents and Count_home_relocations aggregates

Home locations - Changes to the number of resident subscribers per region

Number of subscribers that are assigned to a region as their home region.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • Count_residents

Home locations - changes to the number of subscribers who move home, per pairs of regions

Number of subscribers whose home location has changed, between any two regions or for specific regions.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • Count_home_relocations

  • Count_events

Home locations - duration of disruption, per region

Average time for a region to get back to its pre-crisis subscriber population size (if at all).

Unit

  • Weeks

CDR aggregate(s) required

  • Count_home_relocations

  • Count_events

  • Count_active_residents

Crowdedness measure

Indicators based on time series of Count_subscribers (15min, urban cluster)

Crowdedness measure - crowd size per cluster

Number of subscribers recorded at each cluster within a 15 minute interval (urban areas only): this measures the size of a ‘crowd’.

Unit

  • % of residents

CDR aggregate(s) required

  • Count_subscribers (15min, urban cluster)

Crowdedness measure - crowd frequency per cluster

Number of ‘crowds’ (defined to be more than X subscribers recorded at the same cluster within a 15 minute interval) recorded each day: this measures the frequency with which crowds congregate.

Unit

  • N per day

CDR aggregate(s) required

  • Count_subscribers (15min, urban cluster)

Population mixing

Indicators based on time series of Count_subscribers (day, local) and Count_subscribers (week, local) and Count_residents (local)

Population mixing - visitors vs residents, for each region

Number of unique subscribers recorded in the region each day/week, normalised by the number of subscribers that have that region assigned to them as their ‘home region’: this is an indicator of how many non-resident ‘outside’ visitors come to the region, relative to the size of the resident population.

Unit

  • % of residents

  • % change relative to baseline

CDR aggregate(s) required

  • Count_subscribers (day, local)

  • Count_residents

  • Count_active_residents

Population mixing - ‘mixing factor’, for each region

Average number of unique visitors each day, averaged over a week, divided by the number of unique subscribers to the region in a week: this indicates the degree to which the same people visit a region each day, versus different people visiting each day which would result in higher ‘mixing’.

Unit

  • % of unique week visitors

  • % change relative to baseline

CDR aggregate(s) required

  • Mean Count_subscribers (day, local) divided by Count_subscribers (week, local)

Intra-regional travel

Indicator based on time series of Count_subscribers (day, local) and Count_subscribers (day, regional)

Intra-regional travel - changes to travel within each region

Average number of sub-regions visited in each region per visitors to the region: this measures the amount of movement within a region.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • Mean Count_subscribers (day, local) divided by Count_subscribers (day, regional)

Inter-regional travel

Indicators based on time series of od_matrix_directed_all_pairs, od_matrix_directed_consecutive_pairs and Count_visits_home_away.

Inter-regional travel - changes to incoming flow to each region

Number of subscribers entering a region from another region.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • od_matrix_directed_consecutive_pairs

  • Count_events

Inter-regional travel - changes to outgoing flow from each region

Number of subscribers leaving a region and travelling to another region.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • od_matrix_directed_consecutive_pairs

  • Count_events

Inter-regional travel - changes to net flow of each region

The difference between incoming and outgoing flows: this measures how subscribers are redistributing amongst regions.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • od_matrix_directed_consecutive_pairs

  • Count_events

Inter-regional travel - changes to the distribution of distances travelled

The median distance (and quartiles) travelled by all subscribers that travel to the region from another region: this indicates whether a lot of people come to the region from nearby regions, or from regions that are farther away.

Can be aggregated across regions.

Unit

  • % change relative to baseline

  • km

CDR aggregate(s) required

  • od_matrix_directed_all_pairs

Inter-regional travel - changes to the dispersion distribution

For each destination region, this is the average percentage of subscribers that originated from each region: this indicates whether a lot of people originate from the same region, or whether there are many origin regions with a few people coming from each one.

Variant: standard deviation of coordinates of origin regions.

Unit

  • % change relative to baseline

  • km

CDR aggregate(s) required

  • od_matrix_directed_all_pairs

Inter-regional travel - changes to the mixing factor

Average ‘mixing factor’ of origin regions: indicates whether visitors are coming from a ‘high-risk’ (or ‘high-contribution’) region.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • od_matrix_directed_all_pairs

Inter-regional travel - changes to the number of regions visited, per home location

Average number of regions visited by the resident subscribers of each region.


Variant

Exposure (or contribution): changes to the number of hotspots visited, per home location

Average number of hotspots visited by the resident subscribers of each region)

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • Count_visits_home_away

Inter-regional travel - changes to the line distance travelled, per home location

Average distance to visited regions by the resident subscribers of each region.

Unit

  • % change relative to baseline

  • km

CDR aggregate(s) required

  • Count_visits_home_away

Inter-regional travel - changes to the dispersion of visited regions per home location

Standard deviation of coordinates of visited regions by the resident subscribers of each region.

Unit

  • % change relative to baseline

  • km

CDR aggregate(s) required

  • Count_visits_home_away

Inter-regional travel - changes to the number of subscribers visiting a single region, per region

More specific indicator on the number of subscribers not crossing admin boundaries.

Unit

  • % change relative to baseline

CDR aggregate(s) required

  • Count_subscribers_single_region

Inter-regional travel - changes to the number of subscribers visiting only their home region, per home region

More specific indicator on the number of subscribers not recorded outside of their home region.

Unit

  • % change relative to baseline

  • km

CDR aggregate(s) required

  • Count_subscribers_home_region

Locations of interest

Locations selected from the analysis of population mixing indicators and the analysis of the graph formed by the inter-regional travel aggregate od_matrix_directed_all_pairs.

Regional connectivity structure: isolated clusters of regions

Are there areas of the country isolated for the rest? (which may be easier to protect).

Unit

  • Names

  • Coordinates

CDR aggregate(s) required

  • od_matrix_directed_all_pairs

Regional connectivity structure: main travel routes

List of locations most connected to each other forming a path through the country (along which the virus may spread).

Unit

  • Names

  • Coordinates

CDR aggregate(s) required

  • od_matrix_directed_all_pairs

Regional connectivity structure: main travel routes through hotspots

Path along which most population mixing is occuring (along which the virus may spread).

Unit

  • Names

  • Coordinates

CDR aggregate(s) required

  • od_matrix_directed_all_pairs

Hotspots: locations of hotspots

Locations with high population mixing values and/or crowdedness.

Unit

  • Coordinates

Indicators required

  • Population mixing indicators

  • Crowdedness indicators

Other type of indicators
Sample size / Data quality indicators

These are not indicators of mobility but serve to control for changes in the CDRs that may lead to a misinterpretation of mobility indicators, and to assess uncertainty from the variations of the sample size (number of events and subscribers used to compute the indicators).


Sample size/data quality indicators - number of events

The total number of calls/SMS/data sessions in each region each hour/day.

This is to provide an indicator of the sample (data) size that we are working with in order to know if the analysis for particular regions and times should be discounted due to insufficient data. It also enables to check whether an increase in ‘subscriber counts’ may actually just be due to the normal number of subscribers using their phone more, and to easily determine if there is an issue with e.g. missing data one day.

Unit

  • N per region per time interval

CDR aggregate(s) required

  • Count_events

Sample size/data quality indicators - ‘residents’ activity level

The proportion of residents in a region who use their phone each hour/day, divided by the total number of residents (where ‘residency’ is defined via a home region): this indicates how active the subscribers in each region are.

Unit

  • % of residents

CDR aggregate(s) required

  • Count_residents

  • Count_active_residents

Sample size/data quality indicators - new subscribers

Percentage of all subscribers who are ‘new’ (appeared in the dataset for the first time within the last week): this provides information about how much data we have for subscribers (to inform statistical validity of analyses).

Unit

  • % of subscribers

CDR aggregate(s) required

  • Count_residents