Econ Papers Daily / 期刊论文
利用进入前后数据识别乙醇工厂进入对玉米价格空间格局的影响：印第安纳州研究
Using pre‐ and post‐entry data to identify the effect of ethanol plant entry on the spatial pattern of corn prices: A study in Indiana
摘要
We estimate the long‐run effect of ethanol plant entry on local corn prices using a long‐horizon difference‐in‐differences framework that combines matching with fixed effects while explicitly accounting for treatment intensity and spatial heterogeneity. We find that entry by an ethanol plant with average capacity relative to local corn supply raises nearby corn prices by approximately 17 cents per bushel. Treatment effects differ substantially across plants: price effects vary little among plants with below‐average capacity but increase sharply as plant capacity rises relative to local corn supply. Price effects also extend beyond 30 miles from the entrant, highlighting the importance of accounting for spatial heterogeneity when evaluating localized demand shocks. The results are robust to matching on pre‐treatment determinants of plant location, excluding a high‐price outlier county, and alternative approaches to accounting for spatial dependence in statistical inference.
中文摘要
我们采用长时差分中的差分框架，结合匹配与固定效应，并明确考虑处理强度与空间异质性，估计乙醇工厂进入对当地玉米价格的长期影响。我们发现，相对于当地玉米供应而言，一座具有平均产能的乙醇工厂进入，会使附近玉米价格每蒲式耳提高约17美分。处理效应在不同工厂之间差异显著：在产能低于平均水平的工厂之间，价格效应变化不大，但随着工厂产能相对于当地玉米供应上升，价格效应急剧增加。价格效应还延伸至进入者30英里之外，凸显了在评估局部需求冲击时考虑空间异质性的重要性。该结果在基于工厂选址预处理决定因素的匹配、排除一个高价异常县，以及在统计推断中考虑空间依赖性的替代方法下均保持稳健。