The Bayesian Additive Classification Tree applied to credit risk modelling

  • Authors:
  • Junni L. Zhang;Wolfgang K. Härdle

  • Affiliations:
  • Department of Business Statistics and Econometrics, Guanghua School of Management, Peking University, Beijing 100871, PR China;Center for Applied Statistics and Economics, Wirtschaftswissenschaftliche Fakultät, Humboldt-Universität zu Berlin, Spandauer Straβe 1, 10178, Berlin, Germany

  • Venue:
  • Computational Statistics & Data Analysis
  • Year:
  • 2010

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Abstract

We propose a new nonlinear classification method based on a Bayesian ''sum-of-trees'' model, the Bayesian Additive Classification Tree (BACT), which extends the Bayesian Additive Regression Tree (BART) method into the classification context. Like BART, the BACT is a Bayesian nonparametric additive model specified by a prior and a likelihood in which the additive components are trees, and it is fitted by an iterative MCMC algorithm. Each of the trees learns a different part of the underlying function relating the dependent variable to the input variables, but the sum of the trees offers a flexible and robust model. Through several benchmark examples, we show that the BACT shows excellent performance. We apply the BACT technique to classify whether firms would be insolvent. This practical example is very important for banks to construct their risk profile and operate successfully. We use the German Creditreform database and classify the solvency status of German firms based on financial statement information. We show that the BACT is a serious competitor to the logit model, CART, the Support Vector Machine, random forest and gradient boosting.