Table 3: The demographic, GP registration and GP organisational explanatory variables.

Demographic variables:
Age on census date (16/11/2020)	Years
Self-reported ethnic group	NHS 16 + 1 classification [25]
Sex	Male, female, other
Deprivation	LSOA level IMD 2019 quintiles
Mobility	Number of different GP registrations in previous 12 months, number of address changes in previous 12 months
GP registration variables:
Age at registration	Years <1, 1–14, 15–29, 30–64, 65–84, 85 and over);
Duration of registration	Days (quartiles)
GP organisational variables:
Commissioner	GP practice Clinical Commissioning Group (CCG)
EHR supplier system	EMIS, SystmOne, or Vision

LSOA = Lower Super Output Area, IMD = Index of Multiple deprivation, CCG = Clinical Commissioning Group, EHR = Electronic Health Record.