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arXiv · 2605.00196

Modeling Stock Returns and Volatility Using Bivariate Gamma Generalized Laplace Law

Tomasz J. Kozubowski·Andrey Sarantsev·James A. Spiker
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Abstract

We consider a generalization of the variance-gamma (generalized asymmetric Laplace) distribution, defined as a normal mean - variance mixture with a gamma mixing distribution. While this model is typically studied in the univariate setting, we assume that the gamma mixing variable is observed alongside the primary variable, resulting in a bivariate framework. In this setting, maximum likelihood estimation becomes significantly simpler than in the standard univariate case, reducing to a form of classical linear regression. We derive explicit expressions for the resulting estimators. For certain parameter configurations, the estimators exhibit nonstandard convergence rates, exceeding the usual square-root rate. Finally, we illustrate the applicability of this model in financial contexts by analyzing stock index returns and associated volatility for several major indices.

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Tomasz J. Kozubowski, Andrey Sarantsev, James A. Spiker. 2026-04-30. Modeling Stock Returns and Volatility Using Bivariate Gamma Generalized Laplace Law. https://arxiv.org/abs/2605.00196

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