An Analysis of Selectivity in the Productivity Evaluation of Biotechnology: An Application to Corn
研究了生物技术杂交品种生产力评估中的选择性偏差，基于1990-2010年威斯康星州玉米产量实验数据，发现转基因杂交品种的部分产量优势源于其常规基因，并分析了市场集中度和采用率对偏差的影响。
We investigate selectivity bias in the evaluation of biotech hybrid productivity. The analysis is applied to experimental data on Wisconsin corn yields from 1990 to 2010. Relying on a Heckman‐like factor that accounts for selectivity, we find evidence of selection bias, indicating that some of the observed yield advantage associated with GM hybrids can be attributed to their conventional genes. We document how the rising market concentration of biotech firms has contributed to increasing selectivity bias in corn yield. The impact, however, is offset by the negative effect of the rising adoption rate of GM corn on selectivity bias.