Purchasing power parity in OECD countries: Nonlinear unit root tests revisited

The aim of this paper is to provide additional evidence on the purchasing power parity empirical fulfilment in a pool of OECD countries. We apply the Harvey et al. (2008) linearity test and the Kruse (2011) nonlinear unit root test. The results point to the fact that the purchasing power parity theory holds in a greater number of countries than has been reported in previous studies.     

The purchasing power parity puzzle is worse than you think

The ‘‘purchasing power parity puzzle’’ is the difficulty of reconciling very high short-term volatility of real exchange rates with very slow rates of mean reversion. The strongest evidence of slow mean reversion comes from least squares estimates of first-order autoregressive models of the long-horizon dollar-sterling real exchange rate. Using median-unbiased estimation methods, we show that these methods underestimate the half-lives of PPP deviations, and thus overestimate the speed of mean reversion. When the specification is amended to allow for serial correlation, the speed of mean reversion falls even further. This makes resolution of the purchasing power parity puzzle more problematic.First version received: May 2003/Final version received: July 2004We thank Lutz Kilian, James Lothian, Mark Taylor, and two anonymous referees for helpful comments and suggestions.     

An empirical examination of long-run purchasing power parity using cointegration techniques

This paper presents an empirical analysis of long-run purchasing power parity (PPP) for five major exchange rates using recently developed econometric techniques on the cointegration of economic time series. Our empirical results are extremely unfavourable to the PPP hypothesis as a long-run equilibrium condition, even with an allowance made for measurement error and/or tranportation costs. In particular, we are unable to reject the hypothesis of non-cointegration of the exchange rate and relative prices for any of the countries concerned. Far from finding a stable, long-run proportionality between exchange rates and relative prices, our results therefore suggest that they tend to drift apart without bound.     

国际购买力平价和简化净出口函数:中国实证

文章从国际交换价值的角度研究了一价定律的内涵,提出了国际购买力平价理论,并且证明了国际购买力平价是严格意义上的均衡汇率。2009年人民币贸易品购买力平价为6.70元人民币/美元,而国际购买力为5.49元人民币/美元,后者可作为确定人民币汇率处于均衡水平的参考。文章还简化了净出口函数,得出如下主要结论:(1)近年我国的贸易顺差大幅增长,主要是因为价格贸易条件恶化,其次是因为J曲线效应;(2)当前的首要任务是改善我国的价格贸易条件以提高国际购买力平价,而不是调整人民币汇率。     

Purchasing Power Parity and Interest Parity in the Laboratory

This paper analyses purchasing power parity and uncovered interest parity in the laboratory. It finds strong evidence that purchasing power parity, covered interest parity, and uncovered interest parity hold. Subjects are endowed with an intrinsically useless (green) currency that can be used to purchase another useless (red) currency. Green goods can be bought only with green currency, and red goods can be bought only with red currency. The foreign exchange markets are organised as call markets. In the treatment analysing purchasing power parity, the price of the red good varies. In a second treatment, the interest rate on red currency varies. In a third treatment, the interest rate on red currency varies, and the price of the red good is random.     

The Impact of Traded Goods Prices on the New Zealand Economy*

Recent empirical work in Australia and New Zealand reveals a diversity of estimates of the dynamic response to changes in traded goods prices. Similarly, there is conflicting evidence as to whether relative purchasing power parity is a characteristic of models estimated from data. In this paper it is argued that a reduced form approach to empirical modelling is appropriate for New Zealand's particular circumstances. The resulting model is simulated in a novel way, with results that argue against the use of a simple traded/non-traded goods distinction in the analysis of foreign price impacts on New Zealand. Purchasing power parity is, however, consistent with the results.     

Half-lives of Deviations from PPP: Contrasting Traded and Nontraded Components of Consumption Baskets

The paper examines the convergence question by contrasting the half‐lives of deviations from purchasing power parity (PPP) across traded and nontraded goods in an exchange rate model with sticky prices. In particular, empirical results show that in most cases the half‐lives of PPP deviations for traded goods are shorter than those for total consumption and for nontraded goods.     

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.     

A managerial model of investment: overlooked alternatives

The long-run purchasing power parity (PPP) hypothesis is tested for nine bilateral sterling exchange rates, using recently developed techniques on cointegration and seasonal integration. The empirical findings show that none of the exchange rates and relative prices contain seasonal unit roots, but all have an autoregressive unit root. The cointegration tests overwhelmingly reject the PPP hypothesis as a long-run equilibrium condition for all countries concerned.     

竞争力平价与人民币均衡汇率研究

传统的汇率决定理论认为，一国货币汇率的衡水平是由购买力平价、利率平价和货币相对供求等决定的。大多数实证研究表明，这些均衡汇率理论只是强调单一因素，同现实相距甚远。本文构建了多因素国际竞争力平价模型，认为均衡实际汇率随着国际竞争力的相对变化而变化，国际竞争力相对提高，该国货币升值，反之则反之。本文利用主成分分析法，从影响人民币汇率的多因素中构造国际竞争力这个指标，实证研究表明人民币实际有效汇率与国际竞争力之间存在协整关系，然后再基于这个协整关系式计算人民币的均衡实际有效汇率，并据以判断人民币汇率偏离均衡水平的程度。     

The purchasing power parity of Southeast Asian currencies: A time-varying coefficient approach

The economies of Southeast Asia have undergone several structural changes, including the Asian currency crisis, during the post-Bretton Woods era. We use a time-varying coefficient cointegration model to test for purchasing power parity (PPP) of Southeast Asian currencies and to track changes in purchasing power relationships over time. The main empirical findings are as follows. First, the stability of the relationship between exchange rates and price differentials is strongly rejected. Second, a major structural change occurs at the outbreak of the Asian currency crisis in 1997. Third, when the cointegration vector is allowed to vary with time, we find evidence of a cointegration relationship for four countries in terms of the US dollar and for four countries in terms of the Japanese yen. Therefore, it seems unlikely that Southeast Asian currencies form a “yen bloc.”     

A wavelet-based panel unit-root test in the presence of an unknown structural break and cross-sectional dependency,with an application of purchasing power parity theory in developing countries

This article introduces two different non-parametric wavelet-based panel unit-root tests in the presence of unknown structural breaks and cross-sectional dependencies in the data. These tests are compared with a previously suggested non-parametric wavelet test, the parameteric Im-Pesaran and Shin (IPS) test and a Wald type of test. The results from the Monte Carlo simulations clearly show that the new wavelet-ratio tests are superior to the traditional tests both in terms of size and power in panel unit-root tests because of its robustness to cross-section dependency and structural breaks. Based on an empirical Central American panel application, we can, in contrast to previous research (where bias due to structural breaks is simply disregarded), find strong, clear-cut support for purchasing power parity (PPP) in this developing region.     

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.     

Monetary Cooperation in Europe and the Problem of Differential Productivity Growth: an argument for a ‘two-speed’ Europe

Cointegration analysis of a productivity-modified purchasing power parity relation supports the hypothesis that—in the long run—the nominal exchange rate adjusts to accommodate different national rates of productivity growth in the traded goods sector. Accordingly, in the long run, an absence of exchange rate flexibility combined with productivity growth differentials is likely to generate an intractable adjustment problem. Because Germany and France display a similar evolution of productivity, this analysis supports their participation in monetary union, whereas a markedly different pattern of productivity growth in the UK constitutes an argument against membership. In passing, we find empirical support for Michael Porter's hypothesis that continuous devaluation can reduce the rate of productivity growth. This also has implications for UK membership.     

Inflation targeting and real exchange rates: A bias correction approach

This paper examines whether inflation targeting (IT) influences purchasing power parity (PPP) by a bias correction approach under cross-sectional dependence. The recursive mean adjustment (RMA) method proposed by So and Shin (1999) and Shin and So (2001) is employed to correct a downward bias in half-life estimates of real exchange rates. More importantly, the empirical results show that IT lowers variability of real exchange rates and plays an important role in providing favorable evidence for long-run PPP.     

Purchasing power parity and relative price variability: Evidence from the 1970s

One curious fact to emerge from the return to flexible exchange rates in the 1970s was the failure of empirical tests of simple versions of the purchasing power parity (PPP) doctrine. This paper seeks to establish whether that observed poor performance of PPP can be attributed to uncertainty regarding the rate of inflation due to the large variations in relative prices experienced during the 1970s. The evidence is found to be unsupportive of the notion.     

人民币汇率升值:历史回顾、动力机制与前景展望

本文回顾了人民币汇率升值的历史进程,剖析了人民币汇率升值的动力机制,并对人民币汇率升值的前景进行了展望。无论从1994年汇率并轨还是从2005年央行重启汇率改革至今,人民币对美元名义汇率以及人民币有效汇率均经历了显著的升值过程。从利率平价、购买力平价、贸易余额与劳动生产率增速等短、中、长期维度来看,人民币对美元汇率依然存在一定的升值动力。下一阶段人民币对美元汇率走势取决于汇率政策制定过程中的博弈。考虑到贸易顺差、短期国际资本流动、输入性通胀与外部压力等因素的消长,下一阶段人民币对美元汇率的升值幅度有望显著放缓(由之前的年均5%～7%放缓至年均2%～3%),并伴随着人民币对美元汇率波动幅度的明显放大。     

Purchasing power parity and real factors

It is acknowledged that purchasing power parity (PPP) fails in empirical tests. The position adopted is that real factors are an omitted variable from the PPP relationship and are the cause of divergences from PPP. The real exchange rate as being determined by supply and demand shift factors (as in Stockman, 1987 and Neary, 1988) is modelled. We then empirically estimate a real exchange rate equation and use the fitted value as a generated regressor in tests of PPP. It is demonstrated that when changes in the real exchange rate are incorporated into the PPP relationship, PPP improves.     

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.     

Non-parametric tests of real exchange rates in the post-Bretton Woods era

This paper examines the mean-reverting property of real exchange rates. Earlier studies have generally not been able to reject the null hypothesis of a unit-root in real exchange rates, especially for the post-Bretton Woods floating period. The results imply that long-run purchasing power parity does not hold. More recent studies, especially those using panel unit-root tests or nonlinear time series models, have found more favorable results, however. But the results from these recent studies are far from conclusive. Consistent individual country time series evidence that supports long-run purchasing power parity continues to be scarce. In this paper, we test for long memory using (Lo’s in Econometrica 59:1279–1313, 1991) the modified rescaled range test, and the rescaled variance test of Giraitis et al. (J Econ 112:265–294, 2003a). Our testing procedure provides a non-parametric alternative to the parametric tests commonly used in this literature. Our data set consists of monthly observations from April 1973 to April 2001 of the G-6 countries (excluding the US) in the OECD. Using the modified rescaled range test, we find only 2 cases out of 15 where the null hypothesis of a unit-root with short-term dependence could be rejected in favor of the alternative hypothesis of long-term dependence and none using the rescaled variance test. Our results therefore do not provide strong empirical support for the stationarity of real exchange rates.