Does a non-linear mean reverting process characterize real GDP movements?

This paper uses non-linear models to investigate non-stationarity of real GDP per capita for seven OECD countries over the period 1900–2000. Unit root tests based on non-linear models are more powerful than traditional ADF statistics in rejecting the null unit root hypothesis. Empirical results show that, contrary to what the linear ADF statistics suggest, stationarity characterizes five out of the seven countries. This finding stands at variance with other recent studies which conclude that movements in real GDP per capita can be characterized as a non-stationary process.

The KPSS test with two structural breaks

In this paper, we generalize the KPSS-type test to allow for two structural breaks. Seven models have been defined depending on the way that structural breaks affect the time series behaviour. The paper derives the limit distribution of the test under both the null and the alternative hypotheses and conducts a set of simulation experiments to analyse the performance in finite samples. Finally, we illustrate the application of the statistics through the analysis of real GDP and real per capita GDP for 22 developed countries.      

GLS detrending-based unit root tests in nonlinear STAR and SETAR models

We extend GLS detrending procedure to testing for unit roots against STAR and SETAR alternatives. Monte Carlo simulations and applications to DM/Yen real exchange rates demonstrate that GLS detrending-based nonlinear unit root tests are more powerful than OLS detrending-based counterparts.     

Deterministic seasonality in Dickey–Fuller tests: should we care?

This paper investigates the properties of Dickey–Fuller tests for seasonally unadjusted quarterly data when deterministic seasonality is present but it is neglected in the test regression. While for the random walk case the answer is straightforward, an extensive Monte Carlo study has to be performed for more realistic processes and testing strategies. The most important conclusion is that the common perception that deterministic seasonality has nothing to do with testing for the long-run properties of the data is incorrect. Further numerical evidence on the shortcomings of the general-to-specific t-sig lag selection method is also presented.

Stabilising Taylor rules when the supply shock has a unit root

This paper studies the implication of unit root supply shocks for the Taylor rule. I find that, when supply shocks have a unit root, if a central bank wishes to guarantee the stationarity of inflation, then their interest rate reaction function should not respond to the output gap. Once the stationarity of inflation is guaranteed by the output-gap-response parameter, the “Taylor principle” can be applied for warranting determinacy of the dynamics.     

A reexamination of the Nelson-Plosser data set using recursive and sequential tests

The present paper applies to the Nelson-Plosser data set the recursive, rolling, and sequential tests proposed by Banerjee, Lumsdaine and Stock (1992) for unit roots in the presence of mean or trend breaks. Unlike Perron's method, these three types of test endogenize the break point in the mean or trend and thus are more appealing in empirical studies. The (reverse) recursive test indicates rejection of the unit root null in industrial production and unemployment rate. The sequential test indicates that nominal GNP and common stock prices are stationary with a break in the mean.Helpful comments from G. S. Maddala and two anonymous referees are greatly acknowledged.     

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.     

INFLATION TARGETING AND THE STATIONARITY OF INFLATION: NEW RESULTS FROM AN ESTAR UNIT ROOT TEST

In this paper, we examine the time series properties of inflation in seven countries that have adopted inflation targeting. Unlike previous studies, we utilize a non‐linear mean reverting adjustment mechanism for inflation and we discover that, although deviations of inflation from the target can exhibit a region of non‐stationary behaviour, overall they are stationary indicating successful targeting implementation.     

The decomposition of Greek real GDP (1858–1938)

In the present article the time series of the decomposition of Greek real GDP are investigated for the presence of a unit root, allowing for a maximum of two breaks which take place at an unknown point in time. This methodology is preferred to the conventional Dickey and Fuller tests because the covered time horizon, namely from 1858 to 1938, is characterized by a number of very important events, the nature of which is either economic or historical.

The out-of-sample performance of an exact median-unbiased estimator for the near-unity AR(1) model

We analyse the forecasting performance of several strategies when estimating the near-unity AR(1) model. We focus on the Andrews’ (1993) exact median-unbiased estimator (BC), the OLS estimator and the driftless random walk (RW). We also explore two pairwise combinations between these strategies. We do this to investigate whether BC helps in reducing forecast errors. Via simulations, we find that BC forecasts typically outperform OLS forecasts. When BC is compared to the RW we obtain mixed results, favouring the latter while the persistence of the true process increases. Interestingly, we find that the combination of BC-RW performs well in a near-unity scheme.     

THE REAL INTEREST RATE DIFFERENTIAL: INTERNATIONAL EVIDENCE BASED ON NON-LINEAR UNIT ROOT TESTS

This paper aims at testing international parity conditions by using non-linear unit root tests advocated by Kapetanios et al . (2003, KSS). Results from the KSS tests based on 17 countries (G7 and 10 Asian countries) overwhelmingly show that the adjustment of real interest rates towards real interest rate parity (RIP) follows a non-linear process except for the Taiwan, Hong Kong and Philippines relationships with both the USA and Japan. Overall, the empirical results are in favour of RIP using the USA and Japan as the centre countries but only if non-linearities are accounted for in the data-generating process. Our findings confirm that interest rate differentials, like the real exchange rates reported in recent literature, display a non-linear mean reversion process.