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Validation of Risk Aggregation in Economic Capital Models
Edited by
David Lynch, Federal Reserve Board of Governors,Iftekhar Hasan, Fordham University Graduate Schools of Business,Akhtar Siddique, Office of the Comptroller of the Currency
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Validation of Models Used by Banks to Estimate Their Allowance for Loan and Lease Losses
Edited by
David Lynch, Federal Reserve Board of Governors,Iftekhar Hasan, Fordham University Graduate Schools of Business,Akhtar Siddique, Office of the Comptroller of the Currency
The Conway–Maxwell–Poisson distribution has garnered interest in and development of other flexible alternatives to classical distributions. This chapter introduces various distributional extensions and generalities motivated by functions of COM–Poisson random variables, including Conway–Maxwell-inspired generalizations of the Skellam distribution, binomial distribution, negative binomial distribution, the Katz class of distributions, two flexible series system life length distributions, and generalizations of the negative hypergeometric distribution.
This chapter considers various models that focus largely on serially dependent variables and the respective methodologies developed with a COM–Poisson underpinning. This chapter first introduces the reader to the various stochastic processes that have been established, including a homogeneous COM–Poisson process, a copula-based COM–Poisson Markov model, and a COM–Poisson hidden Markov model. Meanwhile, there are two approaches for conducting time series analysis on time-dependent count data. One approach assumes that the time dependence occurs with respect to the intensity vector. Under this framework, the usual time series models that assume a continuous variable can be applied. Alternatively, the time series model can be applied directly to the outcomes themselves. Maintaining the discrete nature of the observations, however, requires a different approach referred to as a thinning-based method. Different thinning-based operators can be considered for such models. The chapter then broadens the discussion of dependence to consider COM–Poisson-based spatio-temporal models, thus allowing both for serial and spatial dependence among variables.
Edited by
David Lynch, Federal Reserve Board of Governors,Iftekhar Hasan, Fordham University Graduate Schools of Business,Akhtar Siddique, Office of the Comptroller of the Currency
This chapter examines wholesale credit risk models and their validation at US banking institutions. The most common practice in wholesale credit risk modeling for loss estimation among large US banking institutions today is to use expected loss models, typically at the loan level. The chapter discusses the quantification and validation of three key risk parameters in this modeling approach, namely, probability of default (PD), loss given default (LGD), and exposure at default (EAD).
Edited by
David Lynch, Federal Reserve Board of Governors,Iftekhar Hasan, Fordham University Graduate Schools of Business,Akhtar Siddique, Office of the Comptroller of the Currency
This chapter provides an overview of the validation of models that are used in interest rate risk of the banking book (IRRBB). These includes models used for Funds Transfer Pricing (FTP) as well as asset–liability management (ALM). FTP is a charge (for assets) or a credit (for liabilities) that is charged (credited) by the corporate treasury to the business unit in order to isolate the business unit from market interest rate fluctuations for the life of the asset (liability). ALM involves modeling of principal and interest cash flows – positive cash flows for assets and negative cash flows for liabilities.
Edited by
David Lynch, Federal Reserve Board of Governors,Iftekhar Hasan, Fordham University Graduate Schools of Business,Akhtar Siddique, Office of the Comptroller of the Currency
We study a stochastic differential equation with an unbounded drift and general Hölder continuous noise of order $\lambda \in (0,1)$. The corresponding equation turns out to have a unique solution that, depending on a particular shape of the drift, either stays above some continuous function or has continuous upper and lower bounds. Under some mild assumptions on the noise, we prove that the solution has moments of all orders. In addition, we provide its connection to the solution of some Skorokhod reflection problem. As an illustration of our results and motivation for applications, we also suggest two stochastic volatility models which we regard as generalizations of the CIR and CEV processes. We complete the study by providing a numerical scheme for the solution.
This paper deals with ergodic theorems for particular time-inhomogeneous Markov processes, whose time-inhomogeneity is asymptotically periodic. Under a Lyapunov/minorization condition, it is shown that, for any measurable bounded function f, the time average $\frac{1}{t} \int_0^t f(X_s)ds$ converges in $\mathbb{L}^2$ towards a limiting distribution, starting from any initial distribution for the process $(X_t)_{t \geq 0}$. This convergence can be improved to an almost sure convergence under an additional assumption on the initial measure. This result is then applied to show the existence of a quasi-ergodic distribution for processes absorbed by an asymptotically periodic moving boundary, satisfying a conditional Doeblin condition.