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The main conclusion is that the use of covariates holds considerable promise in the panel data context, much more so than in the time series context. In fact, the use of the covariates not only leads to increased power, but can actually have an order effect on the shrinking neighbourhoods around unity for which power is non-negligible.<\/jats:p>","DOI":"10.1111\/ectj.12118","type":"journal-article","created":{"date-parts":[[2018,8,7]],"date-time":"2018-08-07T04:45:17Z","timestamp":1533617117000},"page":"57-72","source":"Crossref","is-referenced-by-count":8,"title":["Optimal panel unit root testing with covariates"],"prefix":"10.1093","volume":"22","author":[{"given":"Art\u016bras","family":"Juodis","sequence":"first","affiliation":[{"name":"Faculty of Economics and Business, University of Groningen, Nettelbosje 2, 9747 AE Groningen, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Joakim","family":"Westerlund","sequence":"additional","affiliation":[{"name":"Department of Economics, Lund University, Box 7082, 220 07 Lund, Sweden"},{"name":"Centre for Financial Econometrics, Deakin Business School, 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