Table 2 Selection criteria and justification

Inclusion

Quantification of need in provider requirements

Studies needed to assess a population’s need for healthcare quantitively and translate the respective need into provider requirements.

Publication date

All studies between January 1980 and March 2020 were included in the review.

Language

All studies available in English or German were included in the study. No other languages were included to avoid translation errors.

Exclusion

Forecasting supply

Studies that focused on forecasting existing supply with reference to demographic changes only and did not assess any additional need determinants were excluded.

Inpatient care

Due to differences between inpatient and outpatient care (e.g. payment methods), studies that only focused on inpatient care were excluded.

Non-physicians

Studies that investigated only non-physician providers (e.g. physiotherapists or nurse practitioners) were excluded because of differences regarding remuneration and data availability that could lead to biases.

Low- and middle-income countries

Due to significant differences in healthcare resources, provision of health services and health infrastructure that are likely to influence data availability, studies estimating need for healthcare in low- or middle-income countries were excluded.