scholarly journals A note on the irrelevance of unit root tests and cointegration tests

2020 ◽  
Vol 57 (1) ◽  
pp. 85-87
Author(s):  
Moawia Alghalith
Keyword(s):  
Unit Root ◽  
Unit Root Tests ◽  
Standard Unit ◽  
Cointegration Tests

SummaryWe show that, in practice, the standard unit root tests, cointegration tests, and similar tests are unreliable. This conclusion is more generally applicable to other related regression-based tests. In particular, these tests attempt to solve a problem by creating another problem.

scholarly journals Unit Roots in Time Series with Changepoints

2017 ◽  
Vol 6 (6) ◽  
pp. 127
Author(s):  
Ed Herranz ◽  
James Gentle ◽  
George Wang
Keyword(s):  
Time Series ◽  
Unit Root ◽  
Null Hypothesis ◽  
Structural Changes ◽  
Linear Trend ◽  
Unit Root Test ◽  
Unit Roots ◽  
Cointegration Analysis ◽  
Unit Root Tests ◽  
Standard Unit

Many financial time series are nonstationary and are modeled as ARIMA processes; they are integrated processes (I(n)) which can be made stationary (I(0)) via differencing n times. I(1) processes have a unit root in the autoregressive polynomial. Using OLS with unit root processes often leads to spurious results; a cointegration analysis should be used instead. Unit root tests (URT) decrease spurious cointegration. The Augmented Dickey Fuller (ADF) URT fails to reject a false null hypothesis of a unit root under the presence of structural changes in intercept and/or linear trend. The Zivot and Andrews (ZA) (1992) URT was designed for unknown breaks, but not under the null hypothesis. Lee and Strazicich (2003) argued the ZA URT was biased towards stationarity with breaks and proposed a new URT with breaks in the null. When an ARMA(p,q) process with trend and/or drift that is to be tested for unit roots and has changepoints in trend and/or intercept two approaches that can be taken: One approach is to use a unit root test that is robust to changepoints. In this paper we consider two of these URT's, the Lee-Strazicich URT and the Hybrid Bai-Perron ZA URT(Herranz, 2016.)  The other approach we consider is to remove the deterministic components with changepoints using the Bai-Perron breakpoint detection method (1998, 2003), and then use a standard unit root test such as ADF in each segment. This approach does not assume that the entire time series being tested is all I(1) or I(0), as is the case with standard unit root tests. Performances of the tests were compared under various scenarios involving changepoints via simulation studies.  Another type of model for breaks, the Self-Exciting-Threshold-Autoregressive (SETAR) model is also discussed.

Is Germany's GDP Trend-Stationary? A Measurement-With-Theory Approach / Ist das deutsche BIP trendstationär: Ein Measurement-With-Theory Ansatz

2005 ◽  
Vol 225 (1) ◽  
Author(s):  
Bernd Lücke
Keyword(s):  
World War Ii ◽  
Unit Root ◽  
Linear Trend ◽  
Unit Root Tests ◽  
Theory Approach ◽  
World War ◽  
Standard Unit ◽  
Trend Model ◽  
Catch Up ◽  
Stationary Representation

SummaryThe time series properties of German GDP have been re-examined in recent research. Extending the sample to include GDP data from 1950 onwards, some researchers argued in favor of a trend-stationary rather than difference stationary representation of real log GDP. I show that this conclusion is based on an atheoretic trend model underlying the unit root tests. A simple linear trend model fails to take the post World-War II catch-up process properly into account. I use the Solow growth model to discriminate between transitional catch-up dynamics and longrun equilibrium growth. With the proper transformation of GDP data, I am able to use standard unit root tests and find that both ADF and KPSS tests suggest a difference stationary model. This evidence is supported by non-standard unit root tests which allow for polynomial trend representations.

scholarly journals The Effects of R&D and High Technology Exports on Economic Growth: A Comparative Cointegration Analysis for Turkey and South Korea

2016 ◽  
Author(s):  
Ayfer Ustabaş ◽  
Özgür Ömer Ersin
Keyword(s):  
Economic Growth ◽  
South Korea ◽  
Unit Root ◽  
High Technology ◽  
Unit Root Tests ◽  
Gdp Per Capita ◽  
High Tech ◽  
Cointegration Tests ◽  
Short Run ◽  
Per Capita

The importance of technology and research and development (R&D) on economic development through international trade has been discussed in many studies. However, the empirical studies focusing on the role of high technology exports has been limited. The study aims at filling this gap by evaluating the relationship between high technology exports and GDP per capita levels with structural unit root tests and cointegration methodologies for Turkey and South Korea for the 1989-2014 period. The following hypothesis is evaluated: by increasing high technology manufactured goods’ exports, countries could increase their GDP per capita which also requires increased R&D that translates itself as high technology manufactured exports. The empirical methodology is as follows: both GDP per capita and high-tech exports variables are tested with traditional ADF, PP unit root and KPSS stationarity tests. The series are further evaluated with Zivot-Andrews single break and Lee-Strazicich two break unit root tests. The structural break tests are necessary; it is well-known that structural breaks lead to biased results in the traditional unit root and additionally in the cointegration tests. Lastly, both variables are tested for cointegration with Engle-Granger and Johansen tests by incorporating the break dates as exogenous dummy variables. The estimated models are further checked for parameter instability with CUSUM type tests. The results obtained for Turkey and South Korea are slightly different: i. both variables are cointegrated for both countries; ii. For South Korea, the positive impact of high-tech exports on GDP cannot be rejected in the long and short run; ii. This conclusion cannot be obtained for Turkey, iii. the parameter estimates for Turkey hint a limited positive effect of high tech exports in the short-run only. The results suggest that, in the future, Turkey should increase the investments in human capital and R&D directed to high tech exports to which could accelerate the economic growth.

The sustainability of trade accounts of the ASEAN-5 countries

2014 ◽  
Vol 7 (1) ◽  
pp. 51-65
Author(s):  
Olayeni Olaolu Richard ◽  
Aviral Kumar Tiwari
Keyword(s):  
Steady State ◽  
Unit Root ◽  
Unit Root Tests ◽  
Panel Unit Root Tests ◽  
Macroeconomic Policies ◽  
Panel Unit Root ◽  
Content Type ◽  
Long Run ◽  
Equilibrium Relationship ◽  
Cointegration Tests

Purpose – The present study aims to analyse the sustainability of the trade deficits in the Association of Southeast Asian Nations (ASEAN)-5 countries using panel framework during the period from 1965 to 2011. Design/methodology/approach – The paper applied a battery of first- and second-generation panel unit root tests and Pedroni's, Kao and Chiang's, Westerlund, and Di Iorio and Fachin cointegration tests to achieve the objective. Findings – The paper found the evidence of sustainable trade deficit in ASEAN-5 countries while utilizing panel unit root tests as well as panel cointegration tests. Research limitations/implications – The findings have important macroeconomic policies implication for ASEAN-5 countries that these policies had been effective in leading exports and imports to long-run steady-state equilibrium relationship among the ASEAN-5 countries. Originality/value – The main contribution of the paper is to show that the macroeconomic policies of ASEAN-5 countries had been effective in leading exports and imports to long-run steady-state equilibrium relationship. To the authors' best knowledge, in this area, this is the first study in the panel framework for ASEAN countries.

Survey on structural breaks and unit root tests

2020 ◽  
Vol 58 ◽  
pp. 96-141
Author(s):  
A. Skrobotov ◽  
◽  
Keyword(s):  
Unit Root ◽  
Structural Breaks ◽  
Unit Root Tests

scholarly journals UNIT ROOT TEST WITH HIGH-FREQUENCY DATA

2021 ◽  
pp. 1-59
Author(s):  
Sébastien Laurent ◽  
Shuping Shi
Keyword(s):  
Random Walk ◽  
Unit Root ◽  
High Frequency ◽  
Asset Prices ◽  
Composite Index ◽  
Mean Reversion ◽  
Unit Root Tests ◽  
High Frequency Data ◽  
Frequency Data ◽  
Intraday Data

Deviations of asset prices from the random walk dynamic imply the predictability of asset returns and thus have important implications for portfolio construction and risk management. This paper proposes a real-time monitoring device for such deviations using intraday high-frequency data. The proposed procedures are based on unit root tests with in-fill asymptotics but extended to take the empirical features of high-frequency financial data (particularly jumps) into consideration. We derive the limiting distributions of the tests under both the null hypothesis of a random walk with jumps and the alternative of mean reversion/explosiveness with jumps. The limiting results show that ignoring the presence of jumps could potentially lead to severe size distortions of both the standard left-sided (against mean reversion) and right-sided (against explosiveness) unit root tests. The simulation results reveal satisfactory performance of the proposed tests even with data from a relatively short time span. As an illustration, we apply the procedure to the Nasdaq composite index at the 10-minute frequency over two periods: around the peak of the dot-com bubble and during the 2015–2106 stock market sell-off. We find strong evidence of explosiveness in asset prices in late 1999 and mean reversion in late 2015. We also show that accounting for jumps when testing the random walk hypothesis on intraday data is empirically relevant and that ignoring jumps can lead to different conclusions.

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