Many commonly used treatment effects estimators rely on the unconfoundedness assumption (“selection on observables") which is fundamentally non-testable. When evaluating the effects of labor market policies, researchers need to observe variables that affect both treatment participation and...

To tackle mass unemployment and increase participation rates, the German government over recent years has mainly focused on supply side strategies, including 'making work pay' policies. The 2003 Mini-Job reform introduced an extended subsidy of social security contributions for low wage workers....