Kendall Correlation Coefficients for Portfolio Optimization

Fuente: arXiv
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Autores principales: Espana, Tomas, Coz, Victor Le, Smerlak, Matteo
Formato: Preprint
Publicado: 2024
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author Espana, Tomas
Coz, Victor Le
Smerlak, Matteo
author_facet Espana, Tomas
Coz, Victor Le
Smerlak, Matteo
contents Markowitz's optimal portfolio relies on the accurate estimation of correlations between asset returns, a difficult problem when the number of observations is not much larger than the number of assets. Using powerful results from random matrix theory, several schemes have been developed to "clean" the eigenvalues of empirical correlation matrices. By contrast, the (in practice equally important) problem of correctly estimating the eigenvectors of the correlation matrix has received comparatively little attention. Here we discuss a class of correlation estimators generalizing Kendall's rank correlation coefficient which improve the estimation of both eigenvalues and eigenvectors in data-poor regimes. Using both synthetic and real financial data, we show that these generalized correlation coefficients yield Markowitz portfolios with lower out-of-sample risk than those obtained with rotationally invariant estimators. Central to these results is a property shared by all Kendall-like estimators but not with classical correlation coefficients: zero eigenvalues only appear when the number of assets becomes proportional to the square of the number of data points.
format Preprint
id arxiv_https___arxiv_org_abs_2410_17366
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Kendall Correlation Coefficients for Portfolio Optimization
Espana, Tomas
Coz, Victor Le
Smerlak, Matteo
Statistical Finance
Statistical Mechanics
Markowitz's optimal portfolio relies on the accurate estimation of correlations between asset returns, a difficult problem when the number of observations is not much larger than the number of assets. Using powerful results from random matrix theory, several schemes have been developed to "clean" the eigenvalues of empirical correlation matrices. By contrast, the (in practice equally important) problem of correctly estimating the eigenvectors of the correlation matrix has received comparatively little attention. Here we discuss a class of correlation estimators generalizing Kendall's rank correlation coefficient which improve the estimation of both eigenvalues and eigenvectors in data-poor regimes. Using both synthetic and real financial data, we show that these generalized correlation coefficients yield Markowitz portfolios with lower out-of-sample risk than those obtained with rotationally invariant estimators. Central to these results is a property shared by all Kendall-like estimators but not with classical correlation coefficients: zero eigenvalues only appear when the number of assets becomes proportional to the square of the number of data points.
title Kendall Correlation Coefficients for Portfolio Optimization
topic Statistical Finance
Statistical Mechanics
url https://arxiv.org/abs/2410.17366