subject to omitted variable bias despite the inclusion of control variables. If the direction of omitted variable bias were … modest than retrospective studies suggest. Bias appears to be reduced by a differences-in-differences estimator that examines …

subject to omitted variable bias despite the inclusion of control variables. If the direction of omitted variable bias were … modest than retrospective studies suggest. Bias appears to be reduced by a differences-in-differences estimator that examines …

another, making a government-cheerleading bias.tract Body] …

receive in a given subject. Second, the theory section of the paper argues that class size should interact with student …