Testing nonlinearities in economic growth in the OECD countries: an evidence from SETAR and STAR models

This study estimates the Self Exciting Threshold Autoregressive (SETAR) and Smooth Transition Autoregressive (STAR) models and examines the nonlinear and regime switching dynamics of economic growth for a set of 10 OECD countries. The null of linearity in SETAR model is tested using the recursive polynomial F test of Tsay and the bootstrap based supremum, average and exponential average Lagrange Multiplier (LM) tests of Hansen. The F test of Tsay rejects the null of linearity for all the countries, except Spain and Switzerland. The SETAR model of Hansen reinforces the evidence and suggests the rejection of linear model. The STAR model rejects the null of linearity against STAR nonlinearity for all the countries, except Denmark and Switzerland. The sequential F tests for the conditional nulls suggest the LSTAR nonlinearity for Australia, Belgium, France, Sweden and UK, and the ESTAR nonlinearity for Canada, Spain and the USA.     

Nonlinear regression for unit root models with autoregressive errors

This paper shows that the nonlinear least squares estimator for unit root models has the limiting distribution free of nuisance parameters and is more efficient than the augmented Dickey–Fuller estimator when the sum of coefficients for lagged variables is negative.     

Panel unit root tests under cross section dependence with recursive mean adjustment

Utilizing recursive mean adjustment (RMA) we provide two unit root tests: the covariate RMA unit root test and the panel feasible generalized RMA unit root test. The proposed panel unit root tests are precise and powerful, especially when T > N.     

The Phillips unit root tests for polynomials of integrated processes

In this paper, we derive the limiting distributions of the first order serial correlation coefficient and its t-statistic, which are the basis for the non-parametric unit root tests of Phillips (1987), for polynomials of integrated processes. The resulting limiting distributions depend upon nuisance parameters and in general the modification proposed by Phillips (1987), to achieve a nuisance parameter free limiting distribution, is not feasible for polynomials of integrated processes. For the special case of serially uncorrelated innovations, the limiting distributions are nuisance parameter free and are simulated. The distributions shift to the left with increasing variance for increasing polynomial orders.     

Data-dependent selection of the lag truncation parameter in unit root tests of the Phillips-Perron type

The Andrews (Econometrica, 1991, 59, 817–858) plug-in method of heteroscedastic and autocovariance consistent covariance matrix estimation is used to construct estimators of the long-run variance parameter for use in Phillips-Perron unit root tests. This allows the lag truncation parameter to be data dependent. Monte Carlo size and power estimates are obtained suggesting that this apparently natural approach does not provide significant improvements in test performance.     

Unemployment persistence in EU countries: new evidence using bounded unit root tests

We apply a series of bounded unit root tests to revisit the unemployment persistence in eight European Union (EU) countries. We find strong evidence in favour of the hysteresis hypothesis in all the cases. This result can be explained by a reduced labour mobility, a decreasing wage inflation and a high uncertainty regarding the future level of unemployment in the EU countries.     

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.     

Panel LM unit root tests with level and trend shifts

This paper considers a Lagrange multiplier (LM) based panel unit root test that allows for heterogeneous structural breaks in both the intercepts and slopes of a series. We note that many popular time series variables are likely to exhibit changing means and/or trends over time. Given that the usual tests will depend on the nuisance parameters indicating the locations of the trend breaks, we adopt a transformation procedure that makes our new panel unit root tests invariant to the nuisance parameters. To illustrate the importance of the power gain provided by our test, we examine the convergence hypothesis using relative ratios of per capita health care expenditures in 20 OECD countries. Our results provide evidence that the convergence hypothesis is supported.     

A new unit root test based on F-statistic in ESTAR framework

This article proposes a new F-type unit test in the exponential smooth transition autoregressive framework. We derive the asymptotic nonstandard distribution of the proposed test and explore its finite sample properties; simulation results show our test has greater power than the t_kss test proposed by Kapetanios et al.(2003). Finally, an application on the real exchange rates further underpins its superiority.     

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.     

Stabilizing Taylor rules and determinacy under unit root supply shocks: A re-examination

I revisit the stabilizing and determinacy properties of Taylor-type policy rules in the canonical New Keynesian model when allowing for a unit root in the supply shock process. While able to offset inflationary pressure from non-stationary disturbances, interest-rate feedback rules that are unresponsive to fluctuations in the output gap necessarily produce unstable dynamics and explosive volatility for the latter. Specifically, rules fulfilling the Taylor principle are found to enforce the unique (non-stationary) equilibrium featuring well-anchored inflation expectations and immunity to sunspots; yet there exists no equilibrium predicting stationary behavior for both the inflation and output gap series, irrespective of whether the policy stance induces determinacy or indeterminacy. I show this property survives the adoption of forecast-based instrument rules, and also explore the relationship between Taylor-type rules and optimal discretionary policies in this particular New Keynesian environment.     

Testing for a unit root in the presence of stochastic volatility and leverage effect

Previous studies have shown that the stationary and nonstationary time-varying volatilities have different implications on the unit root test. In this paper, we provide a Bayesian unit root test for an AR(1) model with stochastic volatility and leverage effect. Monte Carlo simulations show that the proposed Bayesian unit root test statistic achieves good finite sample properties and is robust to the stationarity of stochastic volatility.     

Expansions and contractions in Brazil, Colombia and Mexico: A view through nonlinear models

The study of asymmetric behavior of macroeconomic variables over business cycles has had a long tradition in economics. In this present work, we find evidence in favor of the hypothesis of having a STAR-type nonlinear asymmetric behavior of the economic activity, over the last two decades, in three Latin American countries: Brazil, Colombia, and Mexico. For Chile and Venezuela, the null hypothesis of a linear process could not be rejected under the method established by Granger and Teräsvirta [Granger, C.W.J., Teräsvirta, T., 1993. Modelling Nonlinear Relationships. Oxford University Press, New York]. Economic activity is proxied by monthly based industrial production indexes. Evidence of asymmetric behavior is also found according to the generalized impulse response functions analysis for the three countries.     

Asymmetric behavior of inflation differentials in the euro area: Evidence from a threshold unit root test

This paper tests the existence of persistent inflation rate differentials in the euro area by employing linear as well nonlinear unit root tests. Besides linear unit root tests, a two-regime threshold unit root test examines the conjecture that inflation rate differentials follow a nonlinear two-regime process towards a threshold, switching from the persistent regime to the transitory one and vice versa. The results imply that threshold nonlinearity is confirmed in 10 out of the 16 cases. However, we have found unit root regime-switching behavior only in six out of the 16 cases under investigation. This finding implies that these inflation rate differentials were persistent when they were low (regime 1), but transitory when they were high (regime 2). This asymmetric behavior can possibly be explained by the different degree of pressure exercised on governments, which is accompanied with different inflation rate differentials. On the contrary, despite the evidence of nonlinearity, the majority of the inflation rate differentials are found to be monotonically persistent. Our results have strong implications for policy makers. In particular, the documented persistency in the inflation rate differentials might have long-run costs in terms of price and macroeconomic stability.     

Optimality in stochastic OLG models: Theory for tests

We consider general OLG economies under uncertainty, with short maturity assets and with dividend paying assets of infinite maturity and fiat money, and study the optimality properties of equilibria with a sequence of asset markets that are sequentially complete. We provide necessary and sufficient conditions, in terms of asset prices and dividends, for equilibria to be conditionally Pareto optimal. These results provide a theoretical basis for empirical investigation.     

The Polish exchange rate system: A unit root and cointegration analysis

In October 1991 Poland has established a crawling peg regime in which the zloty is tied to a currency basket and devalued with a monthly rate of crawl. If the monetary authorities are successful in defending the crawling peg the basket rate measured in Polish zloty is supposed to be stationary. Furthermore, a stable long-run relationship between the zloty-U.S. dollar rate and the basket's value expressed in U.S. dollar is expected to exist. The results of the unit root and cointegration analysis indicate that the monetary authorities have been able to defend the crawling peg for the sample periods under study, although it seems that not all requirements of the exchange rate regime have been met. The foreign exchange markets, however, have not supported the relationships derived from the crawling peg system after the introduction of the free floating system in April 2000.The final version of this paper has been prepared while I was a Jean Monnet Fellow at the European University Institute. I would like to thank the EUI for the award of the Fellowship and its hospitality. Moreover, I am grateful to Helmut Lütkepohl, Anja Schulz, Ralf Brüggemann, and two anonymous referees for many helpful comments and suggestions. I also thank the Deutsche Forschungsgemeinschaft, SFB 373, for financial support.     

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.     

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).     

Testing hysteresis effect in U.S. state unemployment: new evidence using a nonlinear quantile unit root test

We revisit hysteresis effect in the unemployment rate of each of the 52 states of the United States using nonlinear quantile unit root test over the period 1976M1–2016M7. Our results indicate that unemployment rate of the U.S. economy as a whole displays hysteresis effect over recessionary periods. Nineteen out of 52 states display hysteresis behaviour over the period 1976–2016. For the remaining 33 states, we find four types of behaviours. Some states display stationarity behaviour almost in all quantiles. Some display hysteresis over recessionary periods and in contrast some display hysteresis over expansion period.