Google Mobility Trends (2020)

Google provide an overview of what its mobility trends represent and how it's measured here: https://support.google.com/covid19-mobility/answer/9824897?hl=en&ref_topic=9822927

As it describes:
"The data shows how visitors to (or time spent in) categorized places change compared to our baseline days. A baseline day represents a normal value for that day of the week. The baseline day is the median value from the 5week period Jan 3 - Feb 6, 2020.

For each region-category, the baseline isn't a single value-it's 7 individual values. The same number of visitors on 2 different days of the week, result in different percentage changes. So, we recommend the following:

• Don't infer that larger changes mean more visitors or smaller changes mean less visitors.
• Avoid comparing day-to-day changes. Especially weekends with weekdays."

Mobility trends are measured across six broad categories:
(1) Residential: places of residence.
(2) Grocery & Pharmacy stores: places like grocery markets, food warehouses, farmers markets, specialty food shops, drug stores, and pharmacies.
(3) Workplaces: places of work.
(4) Parks: places like local parks, national parks, public beaches, marinas, dog parks, plazas, and public gardens.
(5) Transit stations: places like public transport hubs such as subway, bus, and train stations.
(6) Retail & Recreation: places like restaurants, cafes, shopping centers, theme parks, museums, libraries, and movie theaters.

The 'Residential' category shows a change in duration-the other categories measure a change in total visitors.

This index is smoothed to the rolling 7-day average.