Slippage in the Conservation Reserve Program or Spurious Correlation? A Comment
评论了Wu关于保护储备计划中“滑移”现象的研究，指出其未考虑内生性问题，数据也无法用于估计价格反馈效应。作者通过复制研究并修正计量问题，发现没有令人信服的证据支持滑移的存在。
Abstract The Conservation Reserve Program (CRP) pays farmers about $2 billion per year to retire cropland under ten‐ to fifteen‐year contracts. Recent research by Wu found that slippage—an unintended stimulus of new plantings—offsets some of CRP's environmental benefits. Wu does not account for the endogeneity of CRP enrollments. Furthermore, the data used by Wu cannot be used to estimate slippage arising from a price feedback effect. We replicate Wu's findings, demonstrate the possible presence of spurious correlation, and construct new estimates with corrections for endogeneity and other econometric problems. We find no convincing evidence of slippage.