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.     

Purchasing power parity for 15 Latin American countries: Panel SURKSS test with a Fourier function

This study applies Panel SURKSS test with a Fourier function to investigate the properties of long-run purchasing power parity (PPP) in fifteen Latin American countries over the period of December 1994 to February 2010. The empirical results from the univariate unit root and panel-based unit root tests indicate that PPP does not hold for these fifteen countries under study. However, results from the Panel SURKSS test with a Fourier function indicate that PPP is valid for these fifteen countries, with the exception of Honduras. Our results highlight the importance of incorporating both nonlinearities and structural breaks when testing the validity of long-run PPP. These results have important policy implications for these fifteen Latin American countries under study.     

Revisiting Purchasing Power Parity in OECD

This study revisits Purchasing Power Parity theory (PPP) in the 34 OECD countries during January 1994–August 2013. We use a new panel stationary test with both sharp breaks and smooth shifts, a novel approach to panel unit-root testing, proposed by Bahmani–Oskooee et al. (2014). The results indicate that the PPP holds in half of the 34 OECD countries. These results indicate the importance of proper modelling of both sharp breaks and smooth shifts in real effective exchange rate series of OECD countries.     

Fourier nonlinear quantile unit root test and PPP in Africa

We test the PPP hypothesis in 29 African countries using a newly developed nonlinear Quantile unit root test with a Fourier function which accounts for smooth breaks. Simulation indicates that the proposed new test has higher power than the conventional Quantile unit root test as proposed by Koneker and Xiao (2004). Our empirical results provide support for the PPP hypothesis in 21 out of 29 African countries, a unique discovery using their real effective exchange rates. It appears that incorporating Fourier function to nonlinear Quantile unit root test gets us closer and closer to solving the PPP puzzle in Africa.     

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.     

Revisiting purchasing power parity for African countries: with nonlinear panel unit-root tests

This study applies Panel Seemingly Unrelated Regressions (SUR) Kapetanios et al. (Kapetanios–Shin–Snell (KSS), SURKSS) tests, proposed by Wu and Lee (2009), to investigate the properties of long-run Purchasing Power Parity (PPP) in 15 African countries. The empirical results from the univariate unit root and panel based unit root tests indicate that PPP does not hold for these 15 countries under study. However, Panel SURKSS tests indicate that PPP is valid for four of these 15 countries. These results have important policy implications for these 15 African countries under study.     

Detecting cointegration relationships under nonlinear models: Monte Carlo analysis and some applications

Testing for cointegration in the presence of nonlinear adjustments or structural breaks is important for examining the equilibrium relationship among economic variables. It is known that standard cointegration tests perform poorly when a cointegration relationship has nonlinear adjustments or structural breaks. However, it is not clear how some cointegration tests allowing for nonlinearity perform under other classes of nonlinear cointegration models. This paper investigates which cointegration tests help detect a cointegration relationship with nonlinear adjustments or structural breaks. Our Monte Carlo simulation results demonstrate that the cointegration test with threshold adjustment generally has better power performance under most cointegration relationships with nonlinearity. We also provide empirical applications to the money demand and term structure of the U.S. interest rates. The empirical results show that the test allowing for threshold adjustment provides strong evidence of the cointegration relationships of money demand and the term structure of interest rates.     

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.     

Smooth structural breaks and the stationarity of the yen real exchange rates

This article examines and solves an interesting paradox in the literature that the tests for purchasing power parity (PPP) based on the yen real exchange rates (RERs) refute the PPP hypothesis more often than those with other major currency-based RERs, and the evidence is sensitive to the sample period used. Using a new empirical methodology accounting for both nonlinearity and multiple smooth temporary breaks in the data, we show that the puzzling finding is due to the failure to take into account the long but temporary large rise and fall in the yen RERs. The results illustrate that the yen RERs in the post-Bretton Woods period are likely mean reverting with linear or nonlinear adjustment toward large, long swing type of infrequent smooth temporary changes around constant equilibrium values, supporting the validity of PPP and resolving the paradox.     

Assessing economic convergence in the EU: is there a perspective for the ‘cohesion countries’?

This article analyses the stochastic income convergence within the EU-15. The empirical analysis uses per capita GDP, in PPP and in constant prices of 2005 for the period 1950 to 2010. Apart from the traditional DF type tests we also account for possible structural changes. In this direction, we employ the Zivot-Andrews (1992) and the Lee-Strazicich (1999, 2003) testing procedures, for one and two breaks, endogenously determined. Furthermore, we apply the Carlino and Mills (1993) methodology proposed for the detection of β-convergence. The overall evidence supports the existence of two discrete clubs, the first by the ‘cohesion countries’ (Portugal, Ireland, Greece and Spain) and the second by the remaining members. In particular, there is a clear evidence of convergence within each club, whereas between clubs there is a luck of catching-up effects. Furthermore, investigation of correlation between relative per capita GDP of each country and several factors that are often identified as growth stimulants, namely Total Factor Productivity, FDI, investment and openness confirm, with the exception of Greece, a strong association between these factors and the convergence process. However, progress in the convergence has not been uniform across countries and over time, reflecting the specific interactions between domestic and international factors and their impact on the convergence process of individual countries.     

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.     

Purchasing power parity for fifteen Latin American countries: Stationary test with a Fourier function

This study applies a stationary test with a Fourier function, proposed by Becker et al. (2006), to test the validity of long-run purchasing power parity (PPP) in fifteen Latin American countries over the period of December 1994 to February 2010. The empirical results from the univariate unit root tests indicate that PPP does not hold for these fifteen countries under study. However, a stationary test with a Fourier function indicates that PPP is valid for four of these 15 Latin American countries and they are Brazil, Chile, Ecuador and Uruguay. These results have important policy implications for these fifteen Latin American countries under study.     

Panel cointegration and the neutrality of money

Most econometric methods for testing the proposition of long-run monetary neutrality rely on the assumption that money and real output do not cointegrate, a result that is usually supported by the data. This paper argues that these results can be attributed in part to the low power of univariate tests, and that a violation of the noncointegration assumption is likely to result in a nonrejection of the neutrality proposition. To alleviate this problem, two new and more powerful panel cointegration tests are proposed that can be used under quite general conditions. The empirical results obtained from applying these tests to a panel covering ten countries between 1870 and 1986 suggest money and real output are cointegrated, and hence that the neutrality proposition must be rejected.      

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.     

PPP in the 34 OECD countries: evidence from quantile-based unit root tests with both smooth and sharp breaks

Conventional unit root tests have mostly failed to validate the PPP. Quantile-based unit root tests by previous research have provided some support for the PPP. In this article, we take an additional step and incorporate sharp shifts and smooth breaks into the quantile-based unit root test and re-examine the PPP in each of the 34 OECD countries over the period 1994:01–2016:03. We find support for the PPP in 18 countries of Austria, Chile, Estonia, Finland, France, Germany, Italy, Korea, Mexico, Netherlands, New Zealand, Poland, Portugal, Slovenia, Sweden, Switzerland, Turkey and the United Kingdom.     

Covariate unit root tests under structural change and asymmetric STAR dynamics

In this paper, we intend to develop a new unit root testing procedure. The novelty of this methodology includes (1) accommodating possible trend breaks of unknown number, unknown dates, and unknown form by employing the Fourier form without directly estimating such breaks; (2) considering possible asymmetric STAR adjustments under the alterative; and (3) utilizing related covariates to boost the testing power. The limiting distribution of the test is derived, and the asymptotic critical values are tabulated. Simulation experiments show that the test can deliver robust size for various breaks commonly seen in economic analysis and enjoy high power property, even in small sample sizes encountered in empirical studies. The usefulness of the test is illustrated in an empirical study on the issue of debt sustainability in 18 OECD countries.     

LM cointegration tests allowing for an unknown number of breaks: implications for the forward rate unbiasedness hypothesis

This article extends the Lagrange multiplier (LM) cointegration test proposed by Westerlund and Edgerton (WE 2007) by allowing for an unknown number of breaks. Monte Carlo simulations provide two main results. First, a loss of power in the LM cointegration tests is detected when potential multiple breaks are ignored. Second, the modified testing procedures do not affect the asymptotic distribution and major properties of the tests of WE under the null, but noticeably increase their testing power in presence of multiple breaks. We also provide empirical applications of the proposed tests for the forward rate unbiasedness hypothesis (FRUH). The results reveal that the FRUH does hold when the effects of the multiple structural breaks are taken into account.     

Structural Changes, Common Stochastic Trends, and Unit Roots in Panel Data

This paper studies the problem of unit root testing in the presence of multiple structural changes and common dynamic factors. Structural breaks represent infrequent regime shifts, while dynamic factors capture common shocks underlying the comovement of economic time series. We examine the modified Sargan–Bhargava (MSB) test in the panel data setting and propose ways to handle multiple structural changes and dynamic factors. Properties of the MSB test under these non-standard conditions are derived. For example, the test statistics are shown to be invariant, in the limit, to mean breaks. This invariance does not carry over to breaks in linear trends, where the test statistics will converge to functionals of weighted Brownian bridges. A simplified test statistic is then proposed, which is invariant to both mean and trend breaks. We further study pooled test statistic based on standardization and combination of p -values. Response surfaces for p -values of all test statistics are computed to facilitate the empirical implementation of the proposed methodology. The pooled tests are shown to have good finite sample performance.     

Purchasing power parity with flexible Fourier stationary test for Central and Eastern European countries

This study applies stationary test with a Fourier function proposed by Enders and Lee (2004, 2009) to test the validity of long-run Purchasing Power Parity (PPP) to assess the nonstationary properties of the Real Exchange Rate (RER) for seven Central and Eastern European Countries (CEECs). We find that our approximation has higher power to detect U-shaped breaks and smooth breaks than linear method if the true data generating process of exchange rate is in fact a stationary nonlinear process. We examine the validity of PPP from the nonlinear point of view and provide robust evidence clearly indicating that the PPP holds true for all CEECs. Our findings point out their exchange rate adjustment is mean reversion towards PPP equilibrium values in a nonlinear way.     

For which countries did PPP hold? A multiple testing approach

We employ a multiple testing technique to identify the countries for which purchasing power parity (PPP) held over the last century. The approach controls the multiplicity problem inherent in simultaneously testing for PPP on several time series, thereby avoiding spurious rejections. It has higher power than traditional multiple testing techniques by exploiting the dependence structure between the countries with a bootstrap approach. Our results show that, plausibly, thus controlling for multiplicity leads to a number of rejections of the null that is intermediate between that of traditional multiple testing techniques and that which results if one tests the null on each single time series at some level α. Research supported by Ruhr Graduate School in Economics and DFG under Sonderforschungsbereich 475.