Table 2.
Summary characteristics of included studies (N=17)
| Characteristic | Asia | America | Africa | Europe | Total |
| Study published year | |||||
| 1990–2000 | 0 | 0 | 0 | 0 | 0 |
| 2001–2010 | 1 | 1 | 1 | 0 | 3 |
| 2011–2017 | 10 | 2 | 2 | 1 | 14 |
| Study design | |||||
| DID | 6 | 1 | 2 | 0 | 9 |
| RD | 2 | 0 | 0 | 1 | 3 |
| PSM | 1 | 1 | 0 | 0 | 2 |
| IV | 0 | 1 | 0 | 0 | 1 |
| PSM-DID | 1 | 0 | 0 | 0 | 1 |
| RCT | 1 | 0 | 0 | 0 | 1 |
| Changes in user charges | |||||
| Increasing | 1 | 0 | 0 | 0 | 1 |
| Decreasing | 1 | 0 | 0 | 0 | 1 |
| Introducing | 0 | 0 | 0 | 0 | 0 |
| Abolishing | 8 | 3 | 3 | 1 | 15 |
| Economy*† | |||||
| Upper middle income | 2 | 3 | 1 | 1 | 7 |
| Lower middle income | 7 | 0 | 2 | 0 | 10 |
| Low income | 1 | 0 | 1 | 0 | 2 |
| Health outcomes‡ | |||||
| General health | 7 | 0 | 1 | 1 | 9 |
| Mortality | 2 | 0 | 2 | 0 | 4 |
| Infectious disease–related outcomes | 2 | 0 | 1 | 0 | 3 |
| Chronic condition–related outcomes | 0 | 2 | 0 | 0 | 3 |
| Nutritional outcomes | 0 | 0 | 1 | 0 | 2 |
| Age group of the study population | |||||
| General | 5 | 2 | 0 | 1 | 8 |
| Women | 1 | 0 | 2 | 0 | 3 |
| Children | 3 | 0 | 2 | 0 | 5 |
| Elderly | 0 | 1 | 0 | 0 | 1 |
| Social economic status of the study population§ | |||||
| Poor | 5 | 2 | 0 | 1 | 8 |
| General | 5 | 1 | 3 | 0 | 9 |
*According to World Bank country classification 2016.
†The multicountry analysis consisted of three countries: two middle-income and one low-income countries.
‡The sum of health outcome category may be double entered because some studies evaluated more than one type of health outcome. America in this review included both South and Latin America.
§As defined in the context of the study.
DID, difference-in-difference; IV, instrumental variable; PSM, propensity score matching; RCT, randomised controlled trial; RD, regression discontinuity.