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.     

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.     

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).     

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.     

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.     

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.     

The behavior of Turkish exchange rates: A panel data perspective

This paper investigates the behavior of Turkish exchange rates within the context of purchasing power parity (PPP) hypothesis by means of recent developments in the panel unit root testing procedures for ten Turkish real exchange rates during January 2002–May 2012. The unit root test which accounts for nonlinearity, smooth structural shifts, and cross-section dependency supports that PPP hypothesis holds for Eurozone and European countries (Denmark, Norway, Sweden, Switzerland, and United Kingdom), while it does not hold for non-European trading partners (Canada, Japan, Saudi Arabia, and USA). From the empirical results, we can conclude that PPP hypothesis holds in the countries which have the free trade agreement, while it is violated in the countries in which there are trade barriers and greater distance. The findings therefore provide policy implications for Turkey in determining equilibrium exchange rates with her major trading partners.     

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.     

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.     

The real exchange rate and the black market exchange rate in developing countries

This article tests for the validity of the Purchasing power parity (PPP) theory using both the black market and the official exchange rates for panels with cross sectional dependency. The test is conducted using a newly developed, nonlinear IV panel unit root test that properly handles cross-sectional dependency for thirty-seven developing countries. We find that the null of joint unit root hypothesis is rejected for the whole panel, using the black market exchange rate, and for sub-panels of African and high inflation countries, using either exchange rate. The black market-based real exchange rates are, therefore, shown to provide stronger evidence for the purchasing power parity theory than do the official rates. This finding is consistent with the observation that black market exchange rates better represent market forces and thus are more relevant when testing for the validity of the PPP theory in developing countries.     

An empirical test of purchasing power parity in selected developing countries: a panel data approach

Abstract

This paper examines the empirical validity of Purchasing Power Parity (PPP) for certain large developing economies by using a panel unit root methodology. The test results show that a long run real exchange rate depreciation trend exists in certain developing countries. Without considering this depreciation trend, it is hard to verify the stationarity and to explain the existence of the extremely long half-lives of the real exchange rates. When a linear time trend is included in the tests, the results tend to support the stationarity of the underlying real exchange rate processes, and the half-lives are significantly shorter and their range can be explained by transitory disturbances.     

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.     

Investigation of the nonlinear behaviour in real exchange rates in developing regions

This article examines whether the purchasing power parity (PPP) theory holds or not for the economies in different developing regions located in Africa, Asia and Latin America. In order to investigate this issue, a nonlinear panel unit root test is used to determine if some or all of the real exchange rates in a panel follow a stationary exponential smooth transition autoregressive process. By applying the nonlinear panel unit root test, our results demonstrate an empirical support for the theory of PPP for the economies in developing regions.     

Asymmetry dynamics in real exchange rates: New results on East Asian currencies

This paper provides new evidence on the purchasing power parity (PPP) hypothesis in six East Asian countries. Based on nonlinear unit root tests, we discovered that the results are broadly consistent with the fact that real exchange rates (RERs) follow a nonlinear mean reversion process. We presented new evidence that the adjustment towards the PPP parity is asymmetric (LSTAR process) above and below the equilibrium value in all but one case — the Malaysian ringgit (MYR). The empirical results suggest that it is important that the conventional tests of PPP be amended to take account of asymmetries in the adjustment process in RERs.     

On the joint Fourier–ESTAR testing of PPP

The purchasing power parity (PPP) is the hypothesis that the real exchange rate series are stationary. This study briefly reviews and applies six competing unit root test procedures to test PPP. Reflecting the existing literature, the results are mixed. The Kiliç test is the most favourable while the Kapetanios, Shin, and Snell (KSS) test is the least favourable to PPP and the standard ADF test lies in between. The same conclusion applies to the Fourier extensions of those three tests. The results support a recently suggested F-test for the significance of Fourier terms in unit root test equations.     

Purchasing power parity in transition countries: Sequential panel selection method

This study applies the Sequential Panel Selection Method (SPSM), proposed by Chortareas and Kapetanios (2009) to test the validity of long-run purchasing power parity (PPP) for a sample of 14 transition countries, using real effective exchange rates, from 1994 to 2012 (for both monthly and quarterly data). SPSM classifies the whole panel into a group of stationary series and a group of non-stationary series. In doing so, we can clearly identify how many and which series in the panel are stationary processes. Empirical results from the SPSM using the Panel KSS unit root test (Ucar and Omay, 2009) with a Fourier function indicate that PPP holds true for most of these transition countries studied. Our results have important policy implications for these transition countries under study.     

On PPP,unit roots and panels

In this paper we use a combination of time series unit root and cointegration analysis and the Bai and Ng (Econometrica 72:1127–1187, 2004) factor model approach to assess the purchasing power parity hypothesis for four real exchange rate panels. Our main findings are twofold: First, we find robust evidence for nonstationary common components in the real exchange rate panels and hence no evidence for PPP. Second, the presence of nonstationary common components is consistent with rejections of the unit root null hypothesis when applying a battery of first and second generation panel unit root tests, which are known to be adversely affected in the presence of common nonstationary components.     

Purchasing power parity and country characteristics: Evidence from panel data tests

We examine long-run purchasing power parity (PPP) using panel data methods to test for unit roots in US dollar real exchange rates of 84 countries. We find stronger evidence of PPP in countries more open to trade, closer to the United States, with lower inflation and moderate nominal exchange rate volatility, and with similar economic growth rates as the United States. We also show that PPP holds for panels of European and Latin American countries, but not for African and Asian countries. Our findings demonstrate that country characteristics can help explain both adherence to and deviations from long-run PPP.     

Are real exchange rates nonlinear with a unit root? Evidence on PPP for Italy: a note

In this article, we apply the recently developed threshold autoregression model to examine both linearity and stationarity of Italy's real exchange rate vis-à-vis her six trading partner (G6) countries. Our main finding is that Italy's real exchange rate is a nonlinear process that is not characterized by a unit root process for five of six trading partner countries. This provides strong support for purchasing power parity.