Propensity score based-estimators are commonly used to estimate causal effects in evaluation research. To reduce bias in observational studies researchers might be tempted to include many, perhaps correlated, covariates when estimating the propensity score model. Taking into account that the...

We consider the problem of statistical analysis on assortative matching. The random vector of interests consists of the age and the history of the first passage time of each of the newly-formed pairs. Complete data are not often available, however. Observations in each variate of the random...