Summary of bias-corrected Shepherd efficiency scores by income group (full results in online supplemental material S4)
| Income group | |||||
| Low income | Lower-middle income | Upper-middle income | High income | All countries | |
| Number of countries | 26 | 46 | 49 | 51 | 172 |
| Mean | 0.69 | 0.82 | 0.88 | 0.95 | 0.86 |
| SD | (0.11) | (0.10) | (0.07) | (0.05) | (0.12) |
| Minimum | 0.50 | 0.55 | 0.73 | 0.80 | 0.50 |
| Maximum | 0.86 | 0.96 | 0.97 | 1 | 1 |
| Top 3 | Malawi, Rwanda, Zimbabwe | El Salvador, Samoa, Vietnam | Angola, Bosnia and Herzegovina, Albania | Latvia, Lithuania, United Arab Emirates | Malawi, Rwanda, Zimbabwe |
| Bottom 3 | Mali, Sierra Leone, Afghanistan | Mauritania, Sudan, Yemen | Colombia, Peru, Brazil | Switzerland, Austria, Belgium | Switzerland, Austria, Belgium |