Data derived from mobile phone GPS data provided by Spectus (a mobility and location data provider) who collect GDPR compliant, de-identified data from opted-in users of smartphone apps who have provided informed consent for their anonymized data to be used for research purposes. The data has been aggregated to daily indexed counts of journeys between local authorities (2021 boundaries) in the UK between 2019 and the end of 2021. The data is presented as rounded z-values between each origin-destination pair (including intra-local-authority flows) and the journey count decile. Please see the data profile for full details of the methodology used to produce the dataset.