Beyond Levels and Growth
研究了教师效应持续性假设错误时价值增值估计的偏差，提出一个累积模型来联合估计教师质量及其持续性，并用北卡罗来纳州数据发现仅三分之一同期教师效应延续到下一学年。
Abstract The levels and growth achievement functions make extreme and diametrically opposed assumptions about the rate at which teacher inputs persist. I first show that if these assumptions are incorrect, teacher value-added estimates can be significantly biased. I then develop a tractable, cumulative model of student achievement that allows for the joint estimation of unobserved teacher quality and its persistence. The model can accommodate varying persistence rates, student heterogeneity, and time-varying teacher attributes. I implement the proposed methodology using schooling data from North Carolina, and find that only a third of the contemporaneous teacher effect survives into the next grade.