Arbeitspapier

Shrinkage estimation of large covariance matrices: Keep it simple, statistician?

Under rotation-equivariant decision theory, sample covariance matrix eigenvalues can be optimally shrunk by recombining sample eigenvectors with a (potentially nonlinear) function of the unobservable population covariance matrix. The optimal shape of this function reflects the loss/risk that is to be minimized. We solve the problem of optimal covariance matrix estimation under a variety of loss functions motivated by statistical precedent, probability theory, and differential geometry. A key ingredient of our nonlinear shrinkage methodology is a new estimator of the angle between sample and population eigenvectors, without making strong assumptions on the population eigenvalues. We also introduce a broad family of covariance matrix estimators that can handle all regular functional transformations of the population covariance matrix under large-dimensional asymptotics. In addition, we compare via Monte Carlo simulations our methodology to two simpler ones from the literature, linear shrinkage and shrinkage based on the spiked covariance model.

Language
Englisch

Bibliographic citation
Series: Working Paper ; No. 327

Classification
Wirtschaft
Estimation: General
Subject
large-dimensional asymptotics
random matrix theory
rotation equivariance

Event
Geistige Schöpfung
(who)
Ledoit, Olivier
Wolf, Michael
Event
Veröffentlichung
(who)
University of Zurich, Department of Economics
(where)
Zurich
(when)
2020

DOI
doi:10.5167/uzh-172202
Handle
Last update
10.03.2025, 11:44 AM CET

Data provider

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Object type

  • Arbeitspapier

Associated

  • Ledoit, Olivier
  • Wolf, Michael
  • University of Zurich, Department of Economics

Time of origin

  • 2020

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