{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T20:46:27Z","timestamp":1786999587054,"version":"build-2736575974"},"reference-count":23,"publisher":"Cambridge University Press (CUP)","issue":"1","license":[{"start":{"date-parts":[[2019,3,29]],"date-time":"2019-03-29T00:00:00Z","timestamp":1553817600000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/www.cambridge.org\/core\/terms"},{"start":{"date-parts":[[2019,3,29]],"date-time":"2019-03-29T00:00:00Z","timestamp":1553817600000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/www.cambridge.org\/core\/terms"}],"content-domain":{"domain":["www.cambridge.org"],"crossmark-restriction":true},"short-container-title":["Econom. Theory"],"published-print":{"date-parts":[[2020,2]]},"abstract":"<jats:p>\n                    This article considers the problem of testing for an explosive bubble in financial data in the presence of time-varying volatility. We propose a sign-based variant of the Phillips, Shi, and Yu (2015,\n                    <jats:italic>International Economic Review<\/jats:italic>\n                    56, 1043\u20131077) test. Unlike the original test, the sign-based test does not require bootstrap-type methods to control size in the presence of time-varying volatility. Under a locally explosive alternative, the sign-based test delivers higher power than the original test for many time-varying volatility and bubble specifications. However, since the original test can still outperform the sign-based one for some specifications, we also propose a union of rejections procedure that combines the original and sign-based tests, employing a wild bootstrap to control size. This is shown to capture most of the power available from the better performing of the two tests. We also show how a sign-based statistic can be used to date the bubble start and end points. An empirical illustration using Bitcoin price data is provided.\n                  <\/jats:p>","DOI":"10.1017\/s0266466619000057","type":"journal-article","created":{"date-parts":[[2019,3,29]],"date-time":"2019-03-29T05:10:41Z","timestamp":1553836241000},"page":"122-169","update-policy":"https:\/\/doi.org\/10.1017\/policypage","source":"Crossref","is-referenced-by-count":36,"title":["SIGN-BASED UNIT ROOT TESTS FOR EXPLOSIVE FINANCIAL BUBBLES IN THE PRESENCE OF DETERMINISTICALLY TIME-VARYING VOLATILITY"],"prefix":"10.1017","volume":"36","author":[{"given":"David I.","family":"Harvey","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stephen J.","family":"Leybourne","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yang","family":"Zu","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"56","published-online":{"date-parts":[[2019,3,29]]},"reference":[{"key":"S0266466619000057_ref23","volume-title":"Asymptotic Statistics","author":"Van der Vaart","year":"2000"},{"key":"S0266466619000057_ref22","doi-asserted-by":"publisher","DOI":"10.1002\/9780470644560"},{"key":"S0266466619000057_ref20","doi-asserted-by":"publisher","DOI":"10.1111\/jtsa.12427"},{"key":"S0266466619000057_ref18","doi-asserted-by":"publisher","DOI":"10.1016\/S1574-8715(07)00210-2"},{"key":"S0266466619000057_ref17","doi-asserted-by":"publisher","DOI":"10.1111\/j.1468-2354.2010.00625.x"},{"key":"S0266466619000057_ref16","doi-asserted-by":"publisher","DOI":"10.1111\/iere.12132"},{"key":"S0266466619000057_ref15","doi-asserted-by":"publisher","DOI":"10.1111\/obes.12026"},{"key":"S0266466619000057_ref10","doi-asserted-by":"publisher","DOI":"10.1016\/j.jempfin.2015.09.002"},{"key":"S0266466619000057_ref5","doi-asserted-by":"publisher","DOI":"10.1515\/9781400830213"},{"key":"S0266466619000057_ref3","first-page":"194","article-title":"On qualitatively robust sign test in random walk model. 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