Nonlinear regression for unit root models with autoregressive errors

This paper shows that the nonlinear least squares estimator for unit root models has the limiting distribution free of nuisance parameters and is more efficient than the augmented Dickey–Fuller estimator when the sum of coefficients for lagged variables is negative.     

Panel unit root tests under cross section dependence with recursive mean adjustment

Utilizing recursive mean adjustment (RMA) we provide two unit root tests: the covariate RMA unit root test and the panel feasible generalized RMA unit root test. The proposed panel unit root tests are precise and powerful, especially when T > N.     

Data-dependent selection of the lag truncation parameter in unit root tests of the Phillips-Perron type

The Andrews (Econometrica, 1991, 59, 817–858) plug-in method of heteroscedastic and autocovariance consistent covariance matrix estimation is used to construct estimators of the long-run variance parameter for use in Phillips-Perron unit root tests. This allows the lag truncation parameter to be data dependent. Monte Carlo size and power estimates are obtained suggesting that this apparently natural approach does not provide significant improvements in test performance.     

Asymmetric behavior of inflation differentials in the euro area: Evidence from a threshold unit root test

This paper tests the existence of persistent inflation rate differentials in the euro area by employing linear as well nonlinear unit root tests. Besides linear unit root tests, a two-regime threshold unit root test examines the conjecture that inflation rate differentials follow a nonlinear two-regime process towards a threshold, switching from the persistent regime to the transitory one and vice versa. The results imply that threshold nonlinearity is confirmed in 10 out of the 16 cases. However, we have found unit root regime-switching behavior only in six out of the 16 cases under investigation. This finding implies that these inflation rate differentials were persistent when they were low (regime 1), but transitory when they were high (regime 2). This asymmetric behavior can possibly be explained by the different degree of pressure exercised on governments, which is accompanied with different inflation rate differentials. On the contrary, despite the evidence of nonlinearity, the majority of the inflation rate differentials are found to be monotonically persistent. Our results have strong implications for policy makers. In particular, the documented persistency in the inflation rate differentials might have long-run costs in terms of price and macroeconomic stability.     

Optimality in stochastic OLG models: Theory for tests

We consider general OLG economies under uncertainty, with short maturity assets and with dividend paying assets of infinite maturity and fiat money, and study the optimality properties of equilibria with a sequence of asset markets that are sequentially complete. We provide necessary and sufficient conditions, in terms of asset prices and dividends, for equilibria to be conditionally Pareto optimal. These results provide a theoretical basis for empirical investigation.     

The Polish exchange rate system: A unit root and cointegration analysis

In October 1991 Poland has established a crawling peg regime in which the zloty is tied to a currency basket and devalued with a monthly rate of crawl. If the monetary authorities are successful in defending the crawling peg the basket rate measured in Polish zloty is supposed to be stationary. Furthermore, a stable long-run relationship between the zloty-U.S. dollar rate and the basket's value expressed in U.S. dollar is expected to exist. The results of the unit root and cointegration analysis indicate that the monetary authorities have been able to defend the crawling peg for the sample periods under study, although it seems that not all requirements of the exchange rate regime have been met. The foreign exchange markets, however, have not supported the relationships derived from the crawling peg system after the introduction of the free floating system in April 2000.The final version of this paper has been prepared while I was a Jean Monnet Fellow at the European University Institute. I would like to thank the EUI for the award of the Fellowship and its hospitality. Moreover, I am grateful to Helmut Lütkepohl, Anja Schulz, Ralf Brüggemann, and two anonymous referees for many helpful comments and suggestions. I also thank the Deutsche Forschungsgemeinschaft, SFB 373, for financial support.     

Markov-switching models and the unit root hypothesis in real US GDP

I find that real US GDP is better characterized as a trend stationary Markov-switching process than as having a (regime-dependent) unit root. I examine the effects of both assumptions on the analysis of business cycle features and their implications for the persistence of the dynamic response of output to a random disturbance.     

The out-of-sample forecasting performance of nonlinear models of regional housing prices in the US

This article provides out-of-sample forecasts of linear and nonlinear models of US and four Census subregions’ housing prices. The forecasts include the traditional point forecasts, but also include interval and density forecasts, of the housing price distributions. The nonlinear smooth-transition autoregressive model outperforms the linear autoregressive model in point forecasts at longer horizons, but the linear autoregressive and nonlinear smooth-transition autoregressive models perform equally at short horizons. In addition, we generally do not find major differences in performance for the interval and density forecasts between the linear and nonlinear models. Finally, in a dynamic 25-step ex-ante and interval forecasting design, we, once again, do not find major differences between the linear and nonlinear models. In sum, we conclude that when forecasting regional housing prices in the United States, generally the additional costs associated with nonlinear forecasts outweigh the benefits for forecasts only a few months into the future.