ADF检验中滞后长度的选择——基于ARIMA（0，1，q）过程的模拟证据

在进行ADF检验时如何确定最优的滞后长度一直是研究者们关注的问题。最近的研究表明,不同的滞后长度选择方法对ADF检验的统计推断影响很大。本文在已有研究的基础上,模拟了更为一般的ARIMA(0,1,q)过程,分析了在不同的数据生成过程、检验式以及样本容量下,各种滞后长度选择方法对ADF检验功效和实际检验水平的影响,认为修正的信息准则通常具有较合理的实际检验水平,而从一般到特殊法具有更为稳健的ADF检验性质。     

Unit root and cointegration tests on the efficiency and biasedness of forward exchange rates

This paper analyzes the stationarity of spot and forward exchange rates by testing for the presence of unit roots in the autoregressive process of the exchange rate time series. The results of the unit root and cointegration tests for forward exchange rates of six major currencies are inconsistent with earlier studies by others that found the existence of unit roots but the absence of cointegration. Our results show that realized spot rates are cointegrated with past forward rates. Both Dickey-Fuller and Augmented Dickey-Fuller tests affirm the unbiased forward rate hypothesis for 30- and 90-day forward rates. The Augmented Dickey-Fuller tests on the longer term forward rate, however, reveal the existence of cointegration that leads to the rejection of the hypothesis.     

Modified CADF and CIPS Panel Unit Root Statistics with Standard Chi‐squared and Normal Limiting Distributions

In an influential paper Pesaran (‘A simple panel unit root test in presence of cross‐section dependence’, Journal of Applied Econometrics, Vol. 22, pp. 265–312, 2007) proposes two unit root tests for panels with a common factor structure. These are the CADF and CIPS test statistics, which are amongst the most popular test statistics in the literature. One feature of these statistics is that their limiting distributions are highly non‐standard, making for relatively complicated implementation. In this paper, we take this feature as our starting point to develop modified CADF and CIPS test statistics that support standard chi‐squared and normal inference.     

带结构突变的确定趋势的单位根检验方法——兼对中国工农业产品比价的实证分析

存在未知结构突变点的DGP关于结构突变的信息是不完全的,理论上不可能得到媲美标准ADF检验或Perron检验的统计特性,且Perron检验比标准ADF检验更适合于作为其单位根统计量的极限分布。本文以Perron(2009)方法为基础,结合minSSR和FGLS详细讨论结构突变的单位根检验的三个步骤,澄清了很多模糊的认识。以我国工农业产品比价和工农业产品价格指数为例,本文的实证研究发现,中国工农业利益分配格局的重大改变是由国际经济事件造成的冲击引起的。     

资本管制有效性与中国汇率制度改革

本文在利率平价框架下考察了近十年中国资本管制的效力。我们采用比较类似金融工具在国内外市场的收益率、检验未抛补利率平价理论偏差的平稳性两种方法进行分析。研究表明,尽管资本管制的效力随时间推移有所下降,但境内外美元利差的持续存在以及未抛补利率平价理论偏差的非平稳性仍然足以证明中国的资本管制基本有效。资本管制的有效性在盯住制框架下确保了汇率稳定和一定的货币政策自主性,并且使未来汇率制度弹性化改革可以渐进地推进。     

On the Power of GLS-Type Unit Root Tests

Elliott, Rothenberg and Stock (1996), (ERS), present a 'GLS' variant of the Dickey-Fuller (DF) unit root test. Their statistic is approximately point-optimal invariant at a chosen local alternative, and usually displays better finite sample power than the DF test. Following the usual efficiency motive for GLS estimation, the higher finite sample power of the ERS test has often been attributed to the greater accuracy of the estimate of the series' non-stochastic component under stationary alternatives close to the null. This paper shows that the GLS estimates of the non-stochastic component are not, in general, more accurate. The power gain arises from the fact that the GLS statistic's null distribution has a greater positive shift relative to the DF test, than its distribution under relevant alternatives, and this persists even when the GLS estimates of the non stochastics have higher variance than the OLS estimates.     

Panel unit root tests under cross-sectional dependence

In this paper alternative approaches for testing the unit root hypothesis in panel data are considered. First, a robust version of the Dickey-Fuller t -statistic under contemporaneous correlated errors is suggested. Second, the GLS t -statistic is considered, which is based on the t -statistic of the transformed model. The asymptotic power of both tests is compared against a sequence of local alternatives. To adjust for short-run serial correlation of the errors, we propose a pre-whitening procedure that yields a test statistic with a standard normal limiting distribution as N and T tends to infinity. The test procedure is further generalized to accommodate individual specific intercepts or linear time trends. From our Monte Carlo simulations it turns out that the robust OLS t -statistic performs well with respect to size and power, whereas the GLS t -statistic may suffer from severe size distortions in small and moderate sample sizes. The tests are applied to test for a unit root in real exchange rates.     

初始条件对LLC检验局部渐近势的影响研究

本文研究了DF类面板数据单位根LLC检验势受时序数据初始值的影响,推导了DF类面板单位根LLC检验统计量在局部备择假设下的极限分布和局部渐近势函数,发现了面板数据单位根LLC检验统计量局部渐近势在同质性局部备择假设下是初始条件的单调递增函数;小样本蒙特卡罗模拟结果表明,若假定初始条件为零,LLC统计量的检验势将被低估。     

Specification Sensitivity in Right‐Tailed Unit Root Testing for Explosive Behaviour

This article aims to provide some empirical guidelines for the practical implementation of right‐tailed unit root tests, focusing on the recursive right‐tailed ADF test of Phillips et al. (2011b). We analyze and compare the limit theory of the recursive test under different hypotheses and model specifications. The size and power properties of the test under various scenarios are examined and some recommendations for empirical practice are given. Some new results on the consistent estimation of localizing drift exponents are obtained, which are useful in assessing model specification. Empirical applications to stock markets illustrate these specification issues and reveal their practical importance in testing.     

A Simple Panel‐CADF Test for Unit Roots*

In this paper, we propose a simple extension to the panel case of the covariate‐augmented Dickey–Fuller (CADF) test for unit roots developed in Hansen (1995) . The panel test we propose is based on a P values combination approach that takes into account cross‐section dependence. We show that the test has good size properties and gives power gains with respect to other popular panel approaches. An empirical application is carried out for illustration purposes on international data to test the purchasing power parity (PPP) hypothesis.     

Random walks,cointegration, and the transmission of shocks across global real estate and equity markets

This article presents tests of the random walk hypothesis for the U.S. and world commercial real estate markets along with the world stock market through utilizing appropriate market indices. The augmented Dickey-Fuller and Phillips-Perron unit root tests and Cochrane variance ratio test find each of these markets to exhibit random walk behavior. In addition, Johansen-Juselius cointegration tests reveal that the three markets are not cointegrated. The vector autoregressive model shows little or no predictive power in explaining the variation in monthly returns. The generalized impulse response functions suggest that shocks stemming from one market are quickly disseminated to the other markets within two months. (JEL G14, G15)     

Testing for unit roots in the presence of uncertainty over both the trend and initial condition

In this paper we provide a joint treatment of two major problems that surround testing for a unit root in practice: uncertainty as to whether or not a linear deterministic trend is present in the data, and uncertainty as to whether the initial condition of the process is (asymptotically) negligible or not. We suggest decision rules based on the union of rejections of four standard unit root tests (OLS and quasi-differenced demeaned and detrended ADF unit root tests), along with information regarding the magnitude of the trend and initial condition, to allow simultaneously for both trend and initial condition uncertainty.     

Does long-run real interest parity hold among EU countries? Some new panel data evidence

This paper tests for long-run ex post real interest parity (RIP) among the major European Union (EU) countries over the period 1979–1998 using a new test, due to Im, Pesaran, and Shin (1997), that allows one to confirm or reject RIP depending on whether a panel data set comprising real interest differentials is stationary or not. This methodology offers substantial advantages over the univariate Augmented Dickey Fuller (ADF) tests that might accept the null of non-stationarity on account of low test power. Strong evidence of onshore RIP occurs during 1986–1990 and 1993–1998 with the half life of a random shock to parity estimated at 2–3 months. There is no evidence of RIP during 1990–1993 despite the easing of remaining capital controls in 1990.     

我国银行和地产类股票价格的联动性研究

本文采用ADF单位根检验、Granger因果检验、Johansen协整检验等计量方法,对银行类股价和地产类股价变动的的相关关系进行了实证研究,结果发现两者之间存在长期的协整关系,并且银行股指是地产股指变动的原因。     

非线性时序模型LM检验的两类临界值检验统计功效比较

本文基于模拟方法比较了不同非线性时序模型的LM检验的功效和规模，同时也考虑一般化线性检验BDS检验参与比较，目的在于探讨蒙特一卡洛渐近法检验与自举法（bootstrap）检验的两类临界值的统计功效何者更为有效。通过实证与对比分析，结果表明，当样本小于200或自回归系数接近单位根，或者线性性检验是ARCHT或BDS时，就可以考虑应用自举法临界值而非渐近临界值。而且还发现，BDS检验仅在一般性上优于LM检验。     

Unit root tests in panel data: asymptotic and finite-sample properties

We consider pooling cross-section time series data for testing the unit root hypothesis. The degree of persistence in individual regression error, the intercept and trend coefficient are allowed to vary freely across individuals. As both the cross-section and time series dimensions of the panel grow large, the pooled t-statistic has a limiting normal distribution that depends on the regression specification but is free from nuisance parameters. Monte Carlo simulations indicate that the asymptotic results provide a good approximation to the test statistics in panels of moderate size, and that the power of the panel-based unit root test is dramatically higher, compared to performing a separate unit root test for each individual time series.     

上海黄金期货市场有效性的实证分析

黄金因为其兼有货币、商品和金融三大属性的特征历来受到人们的重视。今年年初黄金期货在上海期货交易所的上市,填补了我国长期缺乏金融期货的空白。同时管理层与市场各参与主体对黄金期货给予很高的期望与关注,因此研究上海黄金期货市场的有效性具有重要意义。通过运用ADF单位根检验、协整检验、误差修正模型以及格兰杰因果检验等时间序列与计量经济方法,对上海期货交易所黄金期货市场的有效性进行实证分析。结果表明,上海黄金期货市场尚未达到有效,并且黄金现货价格单向引导期货价格。     

Unit root quantile autoregression testing using covariates

This paper extends unit root tests based on quantile regression proposed by Koenker and Xiao [Koenker, R., Xiao, Z., 2004. Unit root quantile autoregression inference, Journal of the American Statistical Association 99, 775–787] to allow stationary covariates and a linear time trend. The limiting distribution of the test is a convex combination of Dickey–Fuller and standard normal distributions, with weight determined by the correlation between the equation error and the regression covariates. A simulation experiment is described, illustrating the finite sample performance of the unit root test for several types of distributions. The test based on quantile autoregression turns out to be especially advantageous when innovations are heavy-tailed. An application to the CPI-based real exchange rates using four different countries suggests that real exchange rates are not constant unit root processes.     

A robust version of the KPSS test based on indicators

This paper proposes a test of the null hypothesis of stationarity that is robust to the presence of fat-tailed errors. The test statistic is a modified version of the so-called KPSS statistic. The modified statistic uses the “sign” of the data minus the sample median, whereas KPSS used deviations from means. This “indicator” KPSS statistic has the same limit distribution as the standard KPSS statistic under the null, without relying on assumptions about moments, but a different limit distribution under unit root alternatives. The indicator test has lower power than standard KPSS when tails are thin, but higher power when tails are fat.     

The Flexible Fourier Form and Local Generalised Least Squares De‐trended Unit Root Tests*

In two recent papers Enders and Lee (2009) and Becker, Enders and Lee (2006) provide Lagrange multiplier and ordinary least squares de‐trended unit root tests, and stationarity tests, respectively, which incorporate a Fourier approximation element in the deterministic component. Such an approach can prove useful in providing robustness against a variety of breaks in the deterministic trend function of unknown form and number. In this article, we generalize the unit root testing procedure based on local generalized least squares (GLS) de‐trending proposed by Elliott, Rothenberg and Stock (1996) to allow for a Fourier approximation to the unknown deterministic component in the same way. We show that the resulting unit root tests possess good finite sample size and power properties and the test statistics have stable non‐standard distributions, despite the curious result that their limiting null distributions exhibit asymptotic rank deficiency.