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I'm curious how this is possible. The data in question, based on the ADF, we strongly fail to reject the null of a unit root. Yet in natural logs, the series is stationary apparently (ie, reject the null as p-value is 0.00).

But even in natural logs, the ACF shows high persistence, and it may as well be an MA(inf) based on the ACF. Also the PACF has a spike at lag=1, but nothing else anywhere. Hence the ACF/PACF seem to indicate a unit root even in natural logs, but the ADF doesn't.

How come?

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    $\begingroup$ Could you include graphs of the logged series and its ACF/PACF? $\endgroup$ – Richard Hardy Dec 24 '17 at 17:09
  • $\begingroup$ @RichardHardy, sure... Sorry but how do I include graphs, etc.? $\endgroup$ – eBopBob Jan 12 '18 at 17:46
  • $\begingroup$ There is a picture symbol in the top bar when writing/editing an answer/question. $\endgroup$ – Christoph Hanck Jan 26 '18 at 12:30

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