Fixed-order PCA: Theory for Overestimated Factor Models
固定阶PCA:对高维因子模型中高估因子模型的理论
Yuan Liao, Xin Tong, Wanjie Wang, Dacheng Xiu
AI总结 本文研究了在高维因子模型中固定阶PCA的渐近理论,通过引入扩展和压缩映射,证明了估计因子的一致性,并展示了在固定阶下因子增强回归的渐近正态性,为保守的因子数上界提供了理论支持。
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我们开发了高维因子模型中主成分分析(PCA)的渐近理论,其中工作维度R是固定的,并且只需满足R≥r,其中r是真实因子数。基于随机矩阵理论中的各向异性局部定律,我们证明了第r个特征值之外的“额外”经验特征值在渐近上受噪声支配、不相干且几乎正交于因子负载。我们引入了两种旋转,一个扩展的r×R映射H'和一个压缩的R×r映射H⁺,并在两种情况下建立了估计因子的一致性。作为应用,我们分析了因子增强回归用于处理效应推断,并证明对于每个固定的R≥r,具有√T渐近正态性。这些结果为采用保守的因子数上界提供了理论基础,并将分析负担从一致的维度选择转移到更温和的对r的上界约束。
We develop asymptotic theory for principal component analysis (PCA) of a high-dimensional factor model in which the working dimension $R$ is fixed and only required to satisfy $R \ge r$, where $r$ is the true number of factors. Building on anisotropic local laws from random matrix theory, we show that the ``extra'' empirical eigencomponents beyond the $r$-th are asymptotically noise-governed, incoherent, and nearly orthogonal to the factor loadings. We introduce two rotations, an expanded $r\times R$ map $H'$ and a compressed $R\times r$ map $H^{+}$, and establish consistency of the estimated factors under both. As an application, we analyze a factor-augmented regression for treatment-effect inference and prove $\sqrt{T}$-asymptotic normality for every fixed $R \ge r$. These results provide a theoretical underpinning for the common empirical practice of adopting a conservative upper bound on the number of factors, and shift the analytical burden from consistent dimension selection to the milder requirement of bounding $r$ from above.