We consider the momentum threshold autoregressive (MTAR) process and characterize the region of the autoregressive coefficients for geometric ergodicity. The region is a proper subset of the ergodic region of the TAR process. We show that the process is geometrically ergodic inside the region...

When time-series data are positively autocorrelated, mean adjustment using the overall sample mean causes biases for sample autocorrelations and parameter estimates, which decreases the coverage probabilities of confidence intervals. A new method for mean adjustment is proposed, in which a datum...

Semiparametric extensions of the seasonal unit root tests for the model of Dickey et al. (1984, J. Amer. Statist. Assoc. 79, 355) are proposed. Development of semiparametric extensions based on the ordinary least-squares estimator (OLSE) is impossible for the regression of Dickey et al. (1984)...

For seemingly unrelated regression (SUR) models with integrated regressors, two sufficient conditions are identified, under which the ordinary least-squares estimator (OLSE) is asymptotically efficient. The first condition is that every pair of regressor processes are cointegrated in a specific...

A robust sign test is proposed for testing unit roots in cross-sectionally dependent panel data. Large sample Gaussian null asymptotics of the test are established under (fixed N, large T) and, for serially uncorrelated error cases, under (large N, fixed T), where N is the number of panel units...

For panel models with random individual and time effects, locally best invariant (LBI) tests are constructed for the null hypothesis of stationarity against the alternative hypothesis of panel unit root. Finite sample properties of the proposed test and an existing test are compared by a Monte...