Asymptotic behaviour of tests for a unit root against an explosive alternative

We compare the asymptotic local power of upper-tail unit root tests against an explosive alternative based on ordinary least squares (OLS) and quasi-differenced (QD) demeaning/detrending. We find that under an asymptotically negligible initialisation, the QD-based tests are near asymptotically efficient and generally offer superior power to OLS-based approaches; however, the power gains are much more modest than in the lower-tail testing context. We also find that asymptotically non-negligible initial conditions do not affect the power ranking in the same way as they do for lower-tail tests, with the QD-based tests retaining a power advantage in such cases.     

Panel LM unit root tests with level and trend shifts

This paper considers a Lagrange multiplier (LM) based panel unit root test that allows for heterogeneous structural breaks in both the intercepts and slopes of a series. We note that many popular time series variables are likely to exhibit changing means and/or trends over time. Given that the usual tests will depend on the nuisance parameters indicating the locations of the trend breaks, we adopt a transformation procedure that makes our new panel unit root tests invariant to the nuisance parameters. To illustrate the importance of the power gain provided by our test, we examine the convergence hypothesis using relative ratios of per capita health care expenditures in 20 OECD countries. Our results provide evidence that the convergence hypothesis is supported.     

Per capita output convergence across Asian countries: Evidence from covariate unit root test with an endogenous structural break

This study investigates long-run convergence of per capita output across ten Asian countries over 1960 to 2014 by taking advantage of possible economic growth determinants, which may be responsible for setting Asian countries on a long-term steady-state growth path. We simultaneously examine the presence of output convergence in the region, as well as the statistical significance of these economic growth determinants, by using a unit root test with a stationary covariate. In addition, the study allows for the presence of endogenous structural changes in the time series under investigation in order to capture sharp drops in per capita outputs, which may be brought about by influential economic events, such as serious economic slumps in domestic economies or the global financial crises in 1997–98 and 2008–09. The limiting distribution of the covariate unit root test that permits structural breaks is also derived. The results show significant evidence to support the convergence hypothesis. In particular, asymptotically absolute convergence holds among Hong Kong, Korea, Singapore, and Taiwan. In addition, Thailand shows a convergence tendency in terms of asymptotically relative convergence toward Singapore. Malaysia, Indonesia, and India also turn out to converge toward Hong Kong in an asymptotically relative sense. Certain potential growth determinants, such as the trade/GDP ratio, inflation rate, government expenditure/GDP ratio, and quality of human capital, may help these countries achieve and maintain the long-run convergence process toward the reference countries in the region.     

Re-examining the Turkish stock market efficiency: Evidence from nonlinear unit root tests

This paper re-examines the efficient market hypothesis (EMH) in the Turkish stock market by utilizing the recent developments in nonlinear unit root tests. To this end, we first employ the linearity test developed by Harvey et al. (2008) and then carry out the nonlinear ESTAR unit root test recently developed by Kruse (2011). The results show that Borsa Istanbul stock price index series have nonlinear behavior and follow the random walk (non-stationary) process, supporting the EMH in Turkish stock market which has weak-form efficiency.     

Hysteresis in unemployment for 17 OECD countries: Stationary test with a Fourier function

In this empirical study, we apply stationary test with a Fourier function proposed by Becker et al. (2006) to re-examine the hysteresis hypothesis in unemployment for 17 OECD countries over the 1960 to 2009 period. The hysteresis in unemployment is confirmed for most of these 17 OECD countries, with the exception of Australia, Canada, Finland, France, Sweden and the USA, when Becker et al.'s (2006) stationary test with a Fourier function is conducted.     

A modified LLC panel unit root test of the PPP hypothesis

In a recent study, Westerlund (Empir Econ 37:517–531, 2009) shows that the performance of the popular LLC (Levin et al., J Econ 108:1–24, 2002) panel unit root test depends critically on the choice of lag truncation used when correcting for serial correlation, and that it is only when this parameter is set as a function of time that the power raises above size. The purpose of the current paper is to propose a modified test that does not suffer from this drawback. The new test is not only simpler to compute but also superior in terms of small-sample performance, which is illustrated using an example purchasing power parity for less developed countries.     

A note on the use of the LLC panel unit root test

One of the single most cited studies within the field of nonstationary panel data analysis is that of LLC (Levin et al. in J Econom 98:1–24, 2002), in which the authors propose a test for a common unit root in the panel. Using both theoretical arguments and simulation evidence, we show that this test can be misleading unless it is based on the same bandwidth selection rule used by LLC.     

Quantile nonlinear unit root test with covariates and an application to the PPP hypothesis

In this article, we employ the methods initiated by Hansen (1995) to develop new quantile nonlinear unit root tests with covariates. The limiting distributions of our proposed tests are derived, which are dependent on nuisance parameter reflecting the correlation between the equation error and the covariates. To deal with this inferential difficulty, two alternative procedures based on either consistent estimate of the nuisance parameter or bootstrap implementation of the test are proposed. Monte Carlo simulations show that the proposed tests perform very well in finite samples and large power gains can be achieved by including correlated covariates in the testing equation. The proposed tests are applied to the PPP hypothesis. The empirical results indicate that the real exchange rates are not constant unit root processes.     

Tenure security and land-related investment: Evidence from Ethiopia

We use a large data set from Ethiopia that differentiates tenure security and transferability to explore determinants of different types of land-related investment and its possible impact on productivity. While we find some support for endogeneity of investment in trees, this is not the case for terraces. Transfer rights are unambiguously investment-enhancing. The large productivity effect of terracing implies that, even where households undertake investments to increase their tenure security, the level of such investment may be below the social optimum. In Ethiopia, government action to increase tenure security and transferability of land rights can significantly enhance rural investment and productivity.     

Reexamining the PPP hypothesis: A nonlinear asymmetric heterogeneous panel unit root test

In this study, we re-examine the PPP hypothesis in the light of the new developments in the unit root testing literature. The recent theoretical findings have pointed out that the real exchange rate series exhibit asymmetric nonlinear behavior. A unit root test applied to analyze the PPP hypothesis therefore, should also take into account this asymmetry inherent in the real exchange rate. Different unit root tests that consider the presence of these data features have been developed in the time series literature. However, a true attempt to test the PPP hypothesis should take a panel data approach. To this end, we propose a nonlinear heterogeneous panel unit root test where the alternative hypothesis allows for symmetric or asymmetric exponential smooth transition autoregressive nonlinearity and provide its finite sample properties. We apply our test to the real exchange rates of the 15 European Union countries against the US dollar. While the results of the linear and symmetric nonlinear heterogeneous panel unit root tests are against the PPP hypothesis, the asymmetric nonlinear heterogeneous panel test that we propose gives support for the PPP hypothesis as expected. Therefore, the conclusions drawn from the linear panel unit root tests or the nonlinear panel unit root tests that do not take asymmetry into account might be misleading.     

Land tenure and investment incentives: Evidence from West Africa

The existing literature on the relationship between property rights in land and agricultural investment in Africa has given results that are often confusing and contradictory. I make two clarifying contributions to this literature. First, I pull together existing studies and investigate whether the results they find have been affected by research methods or local contexts. Studies with small sample sizes, those that use binary investment measures, and those that control for household fixed effects are less likely to find a statistically significant link between land tenure and investment. Self-reported tenure security has been a poor predictor of investment outcomes. Second, I test for a relationship between land tenure and agricultural investment in nine data sets from West Africa. While the link between tenure and investment is significant for fallow and tree planting, it is less robust for labor use and other inputs, such as manure or chemical fertilizer.     

The FMLS-based CUSUM statistic for testing the null of smooth time-varying cointegration in the presence of a structural break

In this paper we extend the FMLS-based CUSUM cointegration test (Xiao and Phillips, 2002) for testing the smooth time-varying cointegration null hypothesis. For this purpose we use Chebyshev time polynomials to specify time-varying coefficients under the null. We derive the limiting distribution of the statistic, which is pivotal with the order of the Chebyshev time polynomials, and we provide the critical values to conduct the proposed test.     

Enhancing the local power of IVX-based tests in predictive regressions

IVX estimation is used increasingly often in predictive regressions with regressors of unknown persistence. While not exhibiting the second-order bias the OLS estimator has in this setup, IVX estimators have reduced rates of convergence when the regressors are highly persistent. The reduced convergence rates may sometimes lead to power losses in finite samples when testing for no predictability, for instance. The note discusses a simple way of improving the local power of IVX-based tests, consisting of augmenting the predictive regression with the lagged dependent variable. This implies a feed-back loop which strengthens the signal of the IVX instrument without changing its dynamic properties. The proposed augmentation works best when the power loss of IVX would have been maximal compared to the infeasible OLS-based test.     

Official central bank interventions and exchange rate volatility: Evidence from a regime-switching analysis

In this paper, we investigate the effect of central bank interventions on the weekly returns and volatility of the DEM/USD and YEN/USD exchange rate returns. In contrast with previous analyses, we allow for regime-dependent specifications and investigate whether official interventions can explain the observed volatility regime switches. It is found that, depending on the prevailing volatility level, coordinated central bank interventions can lead to either a stabilizing or a destabilizing effect. Our results lead us to challenge the usual view that such interventions always imply increases in volatility.     

A simple panel stationarity test in the presence of serial correlation and a common factor

This paper develops a simple test à la Pesaran (2007) for the null hypothesis of stationarity in heterogeneous panel data with cross-sectional dependence in the form of a common factor in the disturbance. We also allow for serial correlation.     

A note on tests of sphericity and cross-sectional dependence for fixed effects panel model

This paper theoretically explains why bias correction appears in two statistics recently developed by Baltagi et al. (2011, 2012), which are designed to test the sphericity and cross-sectional dependence of the errors in the fixed effects panel model respectively. Our explanation shows that the bias correction is in fact avoidable, which is demonstrated by two corresponding statistics that are newly constructed in this paper. Simulation suggests that our statistics perform as well as the two in Baltagi et al. (2011, 2012). In addition, according to the theories underlying our explanation, we extend a new sphericity test proposed by Fisher et al. (2010) to the fixed effects model. Simulation finds that the test behaves well only if both the cross-sectional and the time series dimension are large.     

The impact of information signals on market prices when agents have non-linear trading rules

Several methods have been developed for filtering seasonal influences and extreme returns in financial and economic time series. The theoretical support for these approaches is rather questionable since it focuses on the effects of shocks on prices and not on their sources. Removing such effects modifies the true generating system of market dynamics because of the non-proportional character of non-linearity. Thus, taking into account that the underlying process of economic time series is highly non-linear we cannot be certain a priori what the impact of new information will be on the dynamic structure of a system. The main contribution of this paper is to demonstrate using the methodology of simulations the eventual distortions in time series data arising from the arrival of news when agents follow non-linear trading strategies. We argue that if news can really modify the dynamical behaviour of a system, then the methodology of filtering exogenous distortions needs to be re-examined.     

Non-linear causality between the stock and real estate markets of Western European countries: Evidence from rank tests

Using the non-parametric rank tests proposed by Breitung (2001), we set out in this study to determine whether any non-linear long-run equilibrium relationship exists between the stock and real estate markets of Western European countries. We go on to adopt the threshold error-correction model (TECM) to determine whether a similar relationship is discernible possibly non-linear functions of the log-price of these two markets. The findings clearly point to the existence of long-run unidirectional and bidirectional causality between the real estate market and the stock market in regions both above and below the threshold level. Finally, we find the existence of both wealth and credit price effects in the real estate markets and stock markets of Western European countries, which thereby offer financial institutions and individual investors in their construction of long-term investment portfolios within these two asset markets.     

Evidence on the Convergence of Per Capita Income: A Comparison of Founder Members of the Association of South East Asian Nations and the South Asian Association of Regional Cooperation

This paper investigates the per capita income convergence patterns of a set of Association of South East Asian Nations (ASEAN) and South Asian Association of Regional Cooperation (SAARC) countries. We obtained a time‐series analysis for stochastic convergence by applying unit‐root tests in the presence of two endogenously‐determined structural breaks. We then supplemented the results by tests that produced evidence for β convergence. The evidence shows that the relative per capita income series of ASEAN‐5 countries were consistent with stochastic convergence and β convergence, but this was not found for SAARC‐5 countries. For the ASEAN‐5 countries, the structural breaks associated with the world oil crisis and the Asian crisis impacted heavily on the convergence/divergence process.     

Unit roots and persistence in the nominal interest rate: a confirmatory analysis applied to the OECD

Abstract.  This paper investigates the stochastic properties of long-term and short-term nominal interest rates for the OECD over the post-war era. For that purpose, we employ univariate unit root tests as well as panel unit root and stationarity tests that explicitly allow for cross-sectional dependence. Overall, we find overwhelming evidence that the nominal interest rate contains a unit root, which may be driven by a stochastic common factor. The computation of half-lives through impulse-response functions also points to a high degree of persistence. This has important implications for the cointegration analysis of the Fisher equation, the uncovered interest parity, and the term structure.