Table 1.

Description of 3 methodologies used to weight patient populations to enable the comparison of spending.

Weighting	Description
Core services [36]	Around £80 billion of NHSa funding per year is distributed to commissioners for “core services”. The core services formula is used to ensure fair distribution of this amount to populations with different characteristics. It has separate components that weight each practice’s population for their need for services, including general and acute, mental health, maternity, community care, and prescription needs. In addition, each population is adjusted for local factors: health care utilization, supply of health care services, pricing, unavoidable costs, unmet need (with premature mortality rate used as a proxy), local deprivation, and costs due to unavoidable smallness.
Core services adapted	Three adaptations were made to the core services methodology to better match the spending data received in the freedom of information request. First, as the spending data received did not include mental health, community, or prescription costs, these elements were removed from the formula. Second, the Babylon GP at Hand population was reweighted by the actual age and sex characteristics as opposed to the estimates provided in the core services file. As Babylon GP at Hand is a fast-growing practice, it was over 3 times the size of the estimation [37]. Third, the core services formula assumes that all Babylon GP at Hand patients live in Hammersmith and Fulham, whereas the majority live in other clinical commissioning groups. To improve the accuracy, the local components from each patient's home residence were used.
Carr-Hill [38,39]	The Carr-Hill weighting is used to distribute the global sum, the largest component of primary care funding. It adjusts the population based on drivers of need, including the consulting time recorded for patients with certain characteristics, local premature mortality rates, market forces (local costs), practices rurality index (though this has been phased out), and the number of nursing home patients registered to the practice.

^aNHS: National Health Service.