An alternative solution to the model structure selection problem

An alternative solution to the model structure selection problem is introduced by conducting a forward search through the many possible candidate model terms initially and then performing an exhaustive all subset model selection on the resulting model. An example is included to demonstrate that this approach leads to dynamically valid nonlinear model

Are apparent findings of nonlinearity due to structural instability in economic time series?

Many modelling issues and policy debates in macroeconomics depend on whether macroeconomic times series are best characterized as linear or nonlinear. If departures from linearity exist, it is important to know whether these are endogenously generated (as in, e.g., a threshold autoregressive model) or whether they merely reflect changing structure over time. We advocate a Bayesian approach and show how such an approach can be implemented in practice. An empirical exercise involving several macroeconomic time series shows that apparent findings of threshold type nonlinearities could be due to structural instability

The Vector Floor and Ceiling Model

This paper motivates and develops a nonlinear extension of the Vector Autoregressive model which we call the Vector Floor and Ceiling model. Bayesian and classical methods for estimation and testing are developed and compared in the context of an application involving U.S. macroeconomic data. In terms of statistical significance both classical and Bayesian methods indicate that the (Gaussian) linear model is inadequate. Using impulse response functions we investigate the economic significance of the statistical analysis. We find evidence of strong nonlinearities in the contemporaneous relationships between the variables and milder evidence of nonlinearity in the conditional mean.Nonlinearity; Bayesian; Vector Autoregression

Private equity premium in a general equilibrium model of uninsurable investment risk

This paper studies the quantitative properties of a general equilibrium model where a continuum of heterogeneous entrepreneurs are subject to aggregate as well as idiosyncratic risks in the presence of a borrowing constraint. The calibrated model matches the highly skewed wealth and income distributions of entrepreneurs. The authors provide an accurate solution to the model despite the significant nonlinearities that are absent in the economy with uninsurable labor income risk. The model is capable of generating the average private equity premium of roughly 3 percent and a low risk-free rate. The model also produces procyclicality of the risk-free rate and countercyclicality of the average private equity premium. The countercyclicality of the average equity premium is largely driven by tightening (loosening) of financing constraints during recessions (booms).Risk ; Private equity ; Business cycles

Time-varying Multi-regime Models Fitting by Genetic Algorithms

Many time series exhibit both nonlinearity and nonstationarity. Though both features have often been taken into account separately, few attempts have been proposed to model them simultaneously. We consider threshold models, and present a general model allowing for different regimes both in time and in levels, where regime transitions may happen according to self-exciting, or smoothly varying, or piecewise linear threshold modeling. Since fitting such a model involves the choice of a large number of structural parameters, we propose a procedure based on genetic algorithms, evaluating models by means of a generalized identification criterion. The performance of the proposed procedure is illustrated with a simulation study and applications to some real data.Nonlinear time series; Nonstationary time series; Threshold model