ON THE BIMODALITY OF THE EXACT DISTRIBUTION OF THE TSLS ESTIMATOR
研究了恰好识别或过度识别线性结构方程中两阶段最小二乘估计量密度出现双峰的条件，分析了弱工具变量、内生性程度和过度识别程度的交互作用。
We investigate the possible bimodality of the density of the two-stage least squares (TSLS) estimator in a just-identified/overidentified linear structural equation. By studying the interaction between weakness of instruments, degree of endogeneity, and degree of overidentification we are able to identify conditions for its existence.I thank Grant Hillier, Patrick Marsh, Don Poskitt, the editor Peter Phillips, and two anonymous referees for useful and encouraging comments.