Capitation payments, which make up about 60% of a typical practice’s income, are calculated using a formula developed by Professor Roy Carr-Hill. "This formula takes into consideration, along with other practice characteristics, individual patients' age, gender and health conditions and calculates a "weighted" count of patients according to need. This means that two practices with the same number of patients may have very different weighted patient numbers due to widely varying patient characteristics and health conditions, and as a result, these practices which may seem to be similar in terms of list size, could receive very different levels of funding".