How teachers' unions affect education production

This study helps to explain why measured school inputs appear to have little effect on student outcomes, particularly for cohorts educated since 1960. Teachers' unionization can explain how public schools simultaneously can have more generous inputs and worse student performance. Using panel data on United States school districts, I identify the effect of teachers' unionization through differences in the timing of collective bargaining, especially timing determined by the passage of state laws that facilitate teachers' unionization. I find that teachers' unions increase school inputs but reduce productivity sufficiently to have a negative overall effect on student performance. Union effects are magnified where schools have market power.