A unit root model for trending time-series energy variables

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In this paper, we propose a GARCH-based unit root test that is flexible enough to account for, (a) trending variables, (b) two endogenous structural breaks, and (c) heteroskedastic data series. Our proposed model is applied to a range of time-series, trending, and heteroskedastic energy variables. Our two main findings are: first, the proposed trend-based GARCH unit root model outperforms a GARCH model without trend; and, second, allowing for a time trend and two endogenous structural breaks are important in practice, for doing so allows us to reject the unit root null hypothesis.

Original languageEnglish
Pages (from-to)391-402
Number of pages12
JournalEnergy Economics
Publication statusPublished - Jul 2015
Externally publishedYes


  • Energy price
  • Structural break
  • Trend
  • Unit root

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