A simple efficient GMM estimator of GARCH models

This paper is concerned with efficient GMM estimation and inference in GARCH models. Sufficient conditions for the estimator to be consistent and asymptotically normal are established for the GARCH(1,1) conditional variance process. In addition efficiency results are obtained in the general framework of the GARCH(1,1)-M regression model.GARCH; GARCH-M; efficient GMM

Specification and estimation of random effects models with serial correlation of general form

This paper is concerned with maximum likelihood based inference in random effects models with serial correlation. Allowing for individual effects we introduce serial correlation of general form in the time effects as well as the idiosyncratic errors. A straightforward maximum likelihood estimator is derived and a coherent model selection strategy is suggested for determining the orders of serial correlation as well as the importance of time and individual effects. The methods are applied to the estimation of a production function for the Japanese chemical industry using a sample of 72 firms observed during 1968-1987. Empirically, our focus is on measuring the returns to scale and technical change for the industry.Panel data; serial correlation; random effects

Maximum-Likelihood Based Inference in the Two-Way Random Effects Model with Serially Correlated Time Effects

This paper considers maximum likelihood estimation and inference in the two-way random effects model with serial correlation. We derive a straightforward maximum likelihood estimator when the time-specific component follow an AR(1) or MA(1) process. The estimator is easily generalized to arbitrary stationary and strictly invertible ARMA processes. Furthermore we derive tests of the null hypothesis of no serial correlation as well as tests for discriminating between the AR(1) and MA(1) specifications. A Monte-Carlo experiment evaluates the finite-sample properties of the estimators and test-statistics

Asymptotic properties of the maximum likelihood estimator of random effects models with serial correlation

This paper considers the large sample behavior of the maximum likelihood estimator of random effects models with serial correlation in the form of AR(1) for the idiosyncratic or time-specific error component. Consistent estimation and asymptotic normality as N and/or T grows large is established for a comprehensive specification which nests these models as well as all commonly used random effects models. When only N or T grows large only a subset of the parameters are consistent and asymptotic normality is established for the consistent subsets.Panel data; serial correlation; random effects

Calculating incremental risk charges: The effect of the liquidity horizon

The recent incremental risk charge addition to the Basel (1996) market risk amend- ment requires banks to estimate, separately, the default and migration risk of their trading portfolios that are exposed to credit risk. The new regulation requires the total regulatory charges for trading books to be computed as the sum of the market risk capi- tal and the incremental risk charge for credit risk. In contrast to Basel II models for the banking book no model is prescribed and banks can use internal models for calculating the incremental risk charge. In the calculation of incremental risk charges a key compo- nent is the choice of the liquidity horizon for traded credits. In this paper we explore the e¤ect of the liquidity horizon on the incremental risk charge. Speci�cally we consider a sample of 28 bonds with di¤erent rating and liquidity horizons to evaluate the impact of the choice of the liquidity horizon for a certain rating class of credits. We �find that choosing the liquidity horizon for a particular credit there are two important effects that needs to be considered. Firstly, for bonds with short liquidity horizons there is a miti- gation effect of preventing the bond from further downgrades by trading it frequently. Secondly, there is the possibility of multiple defaults. Of these two effects the multiple default effect will generally be more pronounced for non investment grade credits as the probability of default is severe even for short liquidity periods. For medium investment grade credits these two effects will in general o¤set and the incremental risk charge will be approximately the same across liquidity horizons. For high quality investment grade credits the effect of the multiple defaults is low for short liquidity horizons as the frequent trading effectively prevents severe downgrades.credit risk; incremental risk charge; liquidity horizon; Basel III

Asymptotics for random effects models with serial correlation

This paper considers the large sample behavior of the maximum likelihood estimator of random effects models. Consistent estimation and asymptotic normality as N and/or T grows large is established for a comprehensive specification which allows for serial correlation in the form of AR(1) for the idiosyncratic or time-specific error component. The consistency and asymptotic normality properties of all commonly used random effects models are obtained as special cases of the comprehensive model. When N or T \rightarrow \infty only a subset of the parameters are consistent and asymptotic normality is established for the consistent subsets.Panel data; error components; consistency; asymptotic normality; maximum likelihood.

Calculating incremental risk charges: The effect of the liquidity horizon

The recent incremental risk charge addition to the Basel (1996) market risk amend- ment requires banks to estimate, separately, the default and migration risk of their trading portfolios that are exposed to credit risk. The new regulation requires the total regulatory charges for trading books to be computed as the sum of the market risk capi- tal and the incremental risk charge for credit risk. In contrast to Basel II models for the banking book no model is prescribed and banks can use internal models for calculating the incremental risk charge. In the calculation of incremental risk charges a key compo- nent is the choice of the liquidity horizon for traded credits. In this paper we explore the e¤ect of the liquidity horizon on the incremental risk charge. Speci�cally we consider a sample of 28 bonds with di¤erent rating and liquidity horizons to evaluate the impact of the choice of the liquidity horizon for a certain rating class of credits. We �find that choosing the liquidity horizon for a particular credit there are two important effects that needs to be considered. Firstly, for bonds with short liquidity horizons there is a miti- gation effect of preventing the bond from further downgrades by trading it frequently. Secondly, there is the possibility of multiple defaults. Of these two effects the multiple default effect will generally be more pronounced for non investment grade credits as the probability of default is severe even for short liquidity periods. For medium investment grade credits these two effects will in general o¤set and the incremental risk charge will be approximately the same across liquidity horizons. For high quality investment grade credits the effect of the multiple defaults is low for short liquidity horizons as the frequent trading effectively prevents severe downgrades

Calculating incremental risk charges: The effect of the liquidity horizon

The recent incremental risk charge addition to the Basel (1996) market risk amend- ment requires banks to estimate, separately, the default and migration risk of their trading portfolios that are exposed to credit risk. The new regulation requires the total regulatory charges for trading books to be computed as the sum of the market risk capi- tal and the incremental risk charge for credit risk. In contrast to Basel II models for the banking book no model is prescribed and banks can use internal models for calculating the incremental risk charge. In the calculation of incremental risk charges a key compo- nent is the choice of the liquidity horizon for traded credits. In this paper we explore the e¤ect of the liquidity horizon on the incremental risk charge. Speci�cally we consider a sample of 28 bonds with di¤erent rating and liquidity horizons to evaluate the impact of the choice of the liquidity horizon for a certain rating class of credits. We �find that choosing the liquidity horizon for a particular credit there are two important effects that needs to be considered. Firstly, for bonds with short liquidity horizons there is a miti- gation effect of preventing the bond from further downgrades by trading it frequently. Secondly, there is the possibility of multiple defaults. Of these two effects the multiple default effect will generally be more pronounced for non investment grade credits as the probability of default is severe even for short liquidity periods. For medium investment grade credits these two effects will in general o¤set and the incremental risk charge will be approximately the same across liquidity horizons. For high quality investment grade credits the effect of the multiple defaults is low for short liquidity horizons as the frequent trading effectively prevents severe downgrades