This paper studies the behaviour of the HEGY tests for quarterly data, for seasonal autoregressive unit roots, when the time series being analysed is deterministic seasonal stationary but exhibits a change in the seasonal pattern. As a by-product, we also analyse the HEGY tests for the...

The temporal aggregation effect on seasonal unit roots and its implications for seasonal unit root testing are discussed. The aggregation effect allows to test with any HEGY-type method for integration at the harmonic frequencies through the Nyquist frequency of properly temporally aggregated series

In this paper, a Bayesian approach is suggested to compare unit root models with stationary autoregressive models when both the level and the error variance are subject to structural changes (known as breaks) of an unknown date. Ignoring structural breaks in the error variance may be responsible...

This paper employs a comprehensive set of “state-of-the-art” unit root tests, including the autoregressive neural network (ARNN) unit root test (Yaya et al. 2021; Oxford Bulletin of Economics and Statistics), to investigate unemployment hysteresis in five European countries: France, Italy, the...

This paper initiates a non-linear fractional unit root test also known as autoregressive neural network–fractional integration (ARNN–FI) test. The test is based on a new multilayer perceptron of a neural network process which is applied in Yaya et al. (2021). Further, to investigate the...

While differencing transformations can eliminate nonstationarity, they typically reduce signal strength and correspondingly reduce rates of convergence in unit root autoregressions. The present paper shows that aggregating moment conditions that are formulated in differences provides an orderly...

In this paper we suggest a Bayesian approach for inferring stationary autoregressive models allowing for possible structural changes (known as breaks) in both the mean and the error variance of economic series occuring at unknown times. Efficient Bayesian inference for the unknown number and...

This paper studies the asymptotic behaviour of the HEGY tests for quarterly data, for nonseasonal and seasonal autoregressive unit roots, when the time series being analysed is trend and deterministic seasonal stationary but exhibits a change in the seasonal pattern. Our results show that,...