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.     

Non-linear quantile unit root test and PPP: more evidence from Africa

It is now a common practice to establish stationarity of the real exchange rate as a sign of purchasing power parity (PPP) hypothesis. In this article, we consider the real effective exchange rates of 29 African countries. When we apply conventional linear unit root tests, we find support for the PPP in eight countries. However, when we shift to the newly introduced non-linear quantile unit root test, support for the PPP increases to 15 countries.     

Structural break,nonlinearity and asymmetry: a re-examination of PPP proposition

In this study, we examine the validity of the PPP proposition for 28 European countries. For this purpose, we propose a new unit root test procedure that allows for both gradual structural breaks and asymmetric nonlinear adjustment towards the equilibrium level. Small-sample properties of the new tests are examined through Monte-Carlo simulations. The simulation results suggest that the new tests have satisfactory size and power properties. We then apply these new tests along with other unit root tests to examine stationarity properties of real exchange rate series of the sample countries. Our tests reject the null of unit root in more cases when compared to alternative tests. Overall, we find that the PPP proposition holds in majority of the European countries examined in this article.     

Exchange rates dynamics revisited: a panel data test of the fractional integration order

We test the possibility that exchange rates from nine developed countries have a unit root against the alternate possibility that they are fractionally integrated. Theoretically, exchange rates are only expected to follow a random walk under restrictive assumptions. However, most traditional unit root tests cannot reject a unit root in exchange rates, and time series tests that allow for fractional integration have given inconclusive results. To increase the power of the test of the integration order we develop two panel data tests of the fractional integration order. Monte Carlo simulations show that these tests are correctly sized and have relatively high power compared to other similar tests. Moreover, our empirical results show that we can reject a unit root in exchange rates with a high probability, but the integration order is close to one. This indicates that exchange rates are mean-reverting, although the reversion is slow, resulting in long swings.     

Quantile unit root test and the PPP in Africa

In this study, we apply the Quantile unit root test and revisit the Purchasing Power Parity (PPP) in 20 African countries using real effective exchange rates over the period 1971Q1 to 2012Q4. While traditional unit root tests fail to reject unit root hypothesis in most of the countries, results from Quantile unit root test reject unit root null hypothesis in Ghana, Mauritius, Niger, South Africa, and Togo, providing support for the PPP at least in these five countries. We further estimate the half-life based on Quantile autoregressive (QAR) model to be about 4.57–7.96 quarters (1–2 year).     

标准化对我国出口贸易的影响

在标准主导国际竞争的时代,标准化已成为影响国际贸易的重要变量。本文选取1991-2010年的样本数据,在利用单位根检验对变量平稳性考察的基础上,采用协整检验方法对我国国家标准增量、外商直接投资额、人民币汇率和我国出口贸易额等变量的长期均衡进行了分析并作了误差修正和Granger因果检验。结果表明,外商直接投资额和人民币汇率与我国出口贸易存在正相关,而我国国家标准增量在短期内对我国出口贸易具有抑制作用,在长期内则对我国出口贸易具有促进作用。     

Testing for Unit Roots in Small Panels with Short-run and Long-run Cross-sectional Dependencies

An IV approach, using as instruments non-linear transformations of the lagged levels, is explored to test for unit roots in panels with general dependency and heterogeneity across cross-sectional units. We allow not only for the cross-sectional dependencies of innovations, but also for the presence of co-integration across cross-sectional levels. Unbalanced panels and panels with differing individual short-run dynamics and cross-sectionally related dynamics are also permitted. We also more carefully formulate the unit root hypotheses in panels. In particular, using order statistics, we make it possible to test for and against the presence of unit roots in some of the individual units for a given panel. The individual IV t -ratios, which are the bases of our tests, are asymptotically and normally distributed and cross-sectionally independent. Therefore, the critical values of the order statistics as well as the usual average statistic can be easily obtained from simple elementary probability computations. We show via a set of simulations that our tests work well, whereas other existing tests fail to perform properly. As an illustration, we apply our tests to the panels of real exchange rates, and find no evidence for the purchasing power parity hypothesis, which is in sharp contrast with the previous studies.     

What can Trigger the Resumption of Economic Growth in a Small Open Economy like Greece: Exports or Inward FDI?

The purpose of this article is to investigate the effect of exports and inward foreign direct investment (FDI) on economic development in Greece, in the long and short run, from 1980 to 2013. This study applies the Ng-Perron and DF-GLS unit root tests to determine the level of integration as well as the autoregressive distributed lag (ARDL) method to identify the long-run relationship. Our analysis confirms the long-run relationship between inward FDI, exports and national income. Our results imply that any policy by the Greek Government aimed at boosting economic development through exports will have to be considered for the long run since Greek authorities cannot rely on exports in the short run. However, inward FDI appears more efficient than exports as far as boosting economic progress in the short run.     

Removal of farm subsidies in a regional economy: a computable general equilibrium analysis

There are a number of studies that examine the purchasing power parity (PPP) hypothesis. The empirical findings from the extant literature for the PPP hypothesis are mixed. This article applies univariate and panel Lagrange Multiplier (LM) unit root tests with one and two structural breaks to real exchange rates for 15 Asian countries. The univariate LM unit root tests find evidence of PPP for two-thirds of the sample. The results from the panel LM unit root test support long-run PPP for the Asian countries in the sample. The results from the LM panel unit root tests differ from those of existing panel unit root tests of PPP for Asian countries that have not allowed for the existence of structural breaks.     

A reappraisal of the evidence on PPP: a systematic investigation into MA roots in panel unit root tests and their implications

Panel unit root tests of real exchange rates—as opposed to univariate tests—usually reject non-stationarity. These tests, however, could be biased if the real exchange rate contained MA roots. Indeed, two independent arguments claim that the real exchange rate, being a sum of a stationary and a non-stationary component, is possibly an ARIMA (1, 1, 1) process. Monte Carlo simulations show how systematic changes in the parameters of the components, of the test equation and of the correlation matrix affect the size of first and second-generation panel unit root tests. Two components of the real exchange rate—the real exchange rate of a single good and a weighted sum of relative prices—are constructed from the data for a panel of countries. Computation of the relevant parameters reveals that panel unit root tests of the real exchange rate are severely oversized, usually much more so than simple augmented Dickey-Fuller tests. Thus, the evidence for purchasing power parity from first and second-generation panel unit root tests may be merely due to extreme size biases.     

Testing for weak-form efficiency of crude palm oil spot and future markets: new evidence from a GARCH unit root test with multiple structural breaks

There is a sizeable literature that tests for weak-form efficiency in commodity and energy spot and future prices. While many studies now allow for multiple structural breaks to address the criticism that conventional unit root tests have low power to reject the unit root null in the presence of structural change, the extant literature overlooks the fact that conventional unit root tests are biased in the presence of conditional heteroscedasticity. We apply a recently developed generalized autoregressive conditional heteroscedasticity (GARCH) unit root test with multiple structural breaks to crude palm oil spot and future prices and find much more evidence against weak-form efficiency than that found using tests that fail to allow for conditional heteroscedasticity. Our results point to the importance of allowing for heteroscedasticity when testing for efficiency in commodity and energy spot and future prices.     

Explosive bubbles in the US–China exchange rate? Evidence from right-tailed unit root tests

In this article we apply novel right-tailed unit root (sup Augmented Dickey-Fuller (SADF) and generalized sup ADF) tests to the China–US exchange rate. The empirical results document that the recent financial crisis in 2008 may be preceded by early warning signs of exuberance. Using the SADF test, evidence of an explosive behavior in the nominal exchange is found from 2005 onwards. This period coincides with both financial reforms in China and early indications of an impending US crisis that both have been reported in the literature. Our findings suggest that such an explosive behavior may be attributable to differences in the relative prices of traded goods. Policy implications are also derived.     

Tests of real interest parity in international currency markets

The purpose of this paper is to examine the behavior of real bilateral exchange rates for major currencies and test the hypothesis of real uncovered interest parity with risk premia, and forward looking expectations. It is plausible that the hypothesis of rational expectations cannot be rejected given the unit root nonstationarity of real exchange rates but it is not unlikely that unit root nonstationarity may be due to rational expectations in foreign exchange markets.     

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.     

Panel asymmetric nonlinear unit root test and PPP in Africa

This study revisits purchasing power parity (PPP) theory for 20 African countries using panel asymmetric nonlinear unit root test proposed by Emirmahmutoglu and Omay (2014), through the sequential panel selection method of Chortareas and Kapetanios (2009). While standard panel unit root tests fail to support the PPP, the empirical results from panel asymmetric nonlinear unit root test do support the PPP. However, additional tests reveal that support in all 20 African countries is mostly due to stationarity of the real effective exchange rates of Ghana and Rwanda where the adjustment process towards equilibrium is nonlinear and asymmetric.     

Digging out the PPP hypothesis: an integrated empirical coverage

We use several popular tests to test the validity of the Purchasing Power Parity (PPP) hypothesis. In particular, we analyze four classes of tests??standard univariate unit root tests, co-integration, panel unit root tests, and unit root tests for nonlinear frameworks??for a dataset consisting of 20 bilateral exchange rates. Through this approach, we ascertain the effectiveness of each methodology in assessing the validity of PPP. Overall, our results suggest little evidence to support PPP. Among the conducted tests, the Panel Analysis of Nonstationarity in the Idiosyncratic and Common components (PANIC) provides the richest insights by disentangling the possible sources of non-stationarity of real exchange rates. The relevance of using price indices with different characteristics is also pinpointed.     

Nonlinear dynamics in exchange rate deviations from the monetary fundamentals: An empirical study

This paper reexamines empirical performance of the monetary exchange rate model with nonlinear dynamics of exchange rate deviation from the monetary fundamentals. First, we apply unit root test of Park and Shintani (2005) to post-Bretton Woods exchange rate data and able to reject the null of unit root deviation from monetary fundamentals against alternative hypothesis of nonlinear stationary process for deutschemark, pound, and Swiss franc. Our empirical results find that exchange rates show high degree of mean-reversion with larger deviation and long periods of overvaluation and undervaluation of dollar. We also find empirical evidence of predictability of the monetary fundamentals at longer horizons.     

Do Malaysian house prices follow a random walk? Evidence from univariate and panel LM unit root tests with one and two structural breaks

In this article we apply univariate and panel Lagrange Multiplier (LM) unit root tests with one and twostructural breaks proposed by Lee and Strazicich (2003, 2004) and Im et al. (2005) to examine housing prices for five different housing price indices (all housing, detached housing, semi-detached housing, terrace housing and high-rise housing) in 14 states of Malaysia to test whether housing prices exhibit a random walk. Our main finding from the univariate LM unit root tests is that for the vast majority of states housing prices follow a stationary process about a segmented trend. The results of the panel LM unit root tests provide overwhelming evidence that house prices are segmented trend reverting.     

Testing a theoretical model of mortgage demand on UK data

This study explores whether the long-run purchasing power parity (PPP) hypothesis holds for selected real exchange rates from Turkish economy during the period 1982M1–2003M12. In addition to conventional unit root tests, five different unit root test procedures have been applied including efficient point-optimal tests, extended M tests and GLS-detrended variants of DF tests, to four monthly real exchange rate series defined in terms of both producer and consumer price indices. The countries analysed are the USA, the UK, Germany and Italy which are major trade partners of Turkey. Mixed evidence is found for the long-run PPP hypothesis when real exchange rate is defined in terms of German DM and Italian Lira. However, the empirical analysis reveals that the PPP hypothesis holds strongly in the long-run for the UK£ and US$ based real exchange rates series using either PPI or CPI. In corroboration with other studies in the literature, the bias correlated half-life estimates suggest relatively faster speeds of adjustment supporting the view that the deviations from the PPP rate dissipate rather quickly for relatively high inflation countries.     

DO REAL INTEREST RATES REALLY CONTAIN A UNIT ROOT? MORE EVIDENCE FROM A BOOTSTRAP COVARIATE UNIT ROOT TEST

This paper re‐examines the empirical finding that international real interest rates usually have a unit root. This conclusion is put forth in Rapach and Weber (2004 ), using the Ng and Perron (2001 ) tests. We use Rudebusch's (1993 ) approach to construct the small sample distributions of the Ng and Perron tests, and calculate their asymptotic sizes, size‐adjusted powers and rejection rates. These numbers show that the lack of power in the Ng and Perron tests might account for the findings of Rapach and Weber (2004 ): that the unit root null cannot be rejected for most OECD countries. Size distortions are mild in the case of Ng and Perron tests for two series, but are serious for the Phillips and Perron Z‐test on inflation rates. We then apply a powerful covariate augmented Dickey–Fuller unit root test to examine the series for which stationarity cannot be determined with the Ng and Perron tests. The bootstrap technique is also used to control possible size distortions. In contrast to the results of Rapach and Weber (2004 ), the bootstrap covariate augmented Dickey–Fuller test yields striking evidence that real interest rates are stationary for 14 of 16 OECD countries, because nominal interest rates are stationary for the 14 countries, while inflation rates are stationary for all countries.