This article investigates power and size of some tests for exogeneity of a binary explanatory variable in count models by conducting extensive Monte Carlo simulations. The tests under consideration are Hausman contrast tests as well as univariate Wald tests, including a new test of notably easy...

The identification of average causal effects of a treatment in observational studies is typically based either on the unconfoundedness assumption or on the availability of an instrument. When available, instruments may also be used to test for the unconfoundedness assumption (exogeneity of the...

We use a natural experiment to show that the presence of an external examiner in standardized school tests reduces the proportion of correct answers in monitored classes by 5.5 to 8.5% - depending on the grade and the test - with respect to classes in schools with no external monitor. We find...

The recent literature on instrumental variables (IV) features models in which agents sort into treatment status on the basis of gains from treatment as well as on baselinepretreatment levels. Components of the gains known to the agents and acted on by them may not be known by the observing...

We use the repeated random assignment of external examiners to school institutes in Italy to investigate whether the effect of external monitoring on test score manipulation persists over time. We find that this effect is still present in the tests taken one year after exposure to the examiners,...

There exists a useful framework for jointly implementing Durbin-Wu-Hausman exogeneity and Sargan-Hansen overidenti cation tests, as a single arti cial regression. This note sets out the framework for linear models and discusses its extension to non-linear models. It also provides an empirical...