  This paper reports on a two-tiered experiment designed to separately identify
the selection and effort margins of pay-for-performance (P4P). At the
recruitment stage, teacher labor markets were randomly assigned to a
'pay-for-percentile' or fixed-wage contract. Once recruits were placed, an
unexpected, incentive-compatible, school-level re-randomization was performed,
so that some teachers who applied for a fixed-wage contract ended up being paid
by P4P, and vice versa. By the second year of the study, the within-year effort
effect of P4P was 0.16 standard deviations of pupil learning, with the total
effect rising to 0.20 standard deviations after allowing for selection.
