Key assumptions of synthetic control methodology
| Assumption | Assessment |
| 1. Treated units and potential control units in the donor pool are similar. | Similar levels in variables known to influence outcome variable (see box 1 for objective and subjective elements of this assessment). |
| 2. There is no contamination – spillover of effects of intervention into potential control units. | Based on background knowledge of researchers. |
| 3. No external shocks in potential control units. | Based on background knowledge of researchers informed by review of trends in outcome variable. |