提出新方法解决非光滑函数在政策评估中的推断难题。
Empirical Likelihood for Nonsmooth Functionals
- 用几何方法重构似然函数,处理非光滑性带来的复杂结构。
- 在最优值函数不唯一时仍能保持推断有效性,避免传统方法的严重误校。
- 适合需严格检验复杂政策效果的研究者使用。
经验似然是一种尊重参数自然边界的推断框架,但现有方法通常要求函数光滑,一旦假设不成立,推断会严重失准。对于政策评估中至关重要的最优值函数,光滑性仅在最优解唯一时成立——而这正是最需要严格推断的情形,即复杂政策带来微小收益时。本文提出一种针对部分非光滑函数的自助经验似然方法。其分析核心是将轮廓似然几何化为得分均值与一个水平集之间的距离,该水平集的形状(由非光滑性模式决定的切锥)决定了渐近分布。不同于依赖对偶最优解泰勒展开的经典证明技术,本方法基于确定性凸规划的性质,可直接应用于非光滑函数。由于普通自助法在非光滑情况下无效,我们推导出一种自适应未知水平集几何结构的修正乘子自助法。
原文摘要 · Abstract (English)
Empirical likelihood is an attractive inferential framework that respects natural parameter boundaries, but existing approaches typically require smoothness of the functional and miscalibrate substantially when these assumptions are violated. For the optimal-value functional central to policy evaluation, smoothness holds only when the optimum is unique -- a condition that fails exactly when rigorous inference is most needed where more complex policies have modest gains. In this work, we develop a bootstrap empirical likelihood method for partially nonsmooth functionals. Our analytic workhorse is a geometric reduction of the profile likelihood to the distance between the score mean and a level set whose shape (a tangent cone given by nonsmoothness patterns) determines the asymptotic distribution. Unlike the classical proof technology based on Taylor expansions on the dual optima, our geometric approach leverages properties of a deterministic convex program and can directly apply to nonsmooth functionals. Since the ordinary bootstrap is not valid in the presence of nonsmoothness, we derive a corrected multiplier bootstrap approach that adapts to the unknown level-set geometry.
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