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 s ince 1960. Teachers' unionization can explain how public schools simul taneously can have more generous inputs and worse student performance. Using panel data on United States school districts, I identify the ef fect of teachers' unionization through differences in the timing of co llective bargaining, especially timing determined by the passage of st ate 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.