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Testing Tail-Index Homogeneity via Exceedance-Covariate Independence

Thomas T. Yang

arXiv 14 Oct 2026 · Econometrics

arXiv:2610.21019 · PDF · Extracted main text

Abstract

We propose a test of whether the tail index of a heavy-tailed outcome is homogeneous across observed covariates. The key observation is that, under tail-index homogeneity, normalized log exceedances are asymptotically independent of the covariates even when tail frequencies vary with them. This leads to a simple-to-implement permutation test based on distance covariance, without estimating conditional tail indices or specifying the form of tail-index heterogeneity. For the global and locally balanced versions, we establish validity for order-statistic thresholds and give conditions for consistency and local power. Local balancing selects extremes within two covariate groups and can improve power when tail selection concentrates the covariates. Simulations illustrate these gains. In French motor insurance data, upper conditional quantiles vary with risk characteristics, but the tail-index tests do not reject a common tail index.

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Most heavily cited references

The works this paper leans on most, across its whole bibliography — not restricted to papers in our corpus. Ranked by composite intensity, which combines how often a work is mentioned, how many sections mention it, and how much of that falls in the main text rather than the appendix.

ReferenceIntensityMentionsSectionsMain text
1Székely, Gábor J. and Rizzo, Maria L. and Bakirov, Nail K (2007) Measuring and Testing Dependence by Correlation of Distances0.7946550%
2Wang, Huixia Judy and Li, Deyuan (2013) Estimation of Extreme Conditional Quantiles Through Power Transformation0.73732100%
3Chernozhukov, Victor (2005) Extremal Quantile Regression0.64422100%
4Kinsvater, Paul and Fried, Roland (2017) Conditional Heavy-Tail Behavior with Applications to Precipitation and River Flow Extremes0.64422100%
5Wang, Huixia Judy and Li, Deyuan and He, Xuming (2012) Estimation of High Conditional Quantiles for Heavy-Tailed Distributions0.64422100%
6de Haan, Laurens and Zhou, Chen (2021) Trends in Extreme Value Indices0.64422100%
7Yang, Thomas T (2026) On the Rank Condition of Tail Index Regressions and a Comparative Study with Extremal Quantile Regression self0.5114225%
8Canay, Ivan A. and Kamat, Vishal (2018) Approximate Permutation Tests and Induced Order Statistics in the Regression Discontinuity Design0.40511100%
9Canay, Ivan A. and Romano, Joseph P. and Shaikh, Azeem M (2017) Randomization Tests Under an Approximate Symmetry Assumption0.40511100%
10Chen, Liujun and Zhou, Chen (2026) High-Dimensional Inference for Extreme Value Indices0.40511100%

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