The Apple semiconductor analyst who keeps crying wolf

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FORTUNE -- Kudos to Asymco's Horace Dediu for spotting the similarity between the two Barrons' headlines at right, one from Dec. 20, 2012, the other from Nov. 11, 2011 -- 13 months earlier.

Both are based on notes by Susquehanna semiconductor analyst Christopher Caso. Both warn clients that signals from his supply chain sources tell him that Apple's (aapl) iPhone sales are going to come up short of the Street's expectations.

Last year's prediction turned out to be spectacularly wrong, as Apple reported blow-out fiscal Q1 earnings on the strength of iPhone sales that grew 128% year over year.

That hasn't stopped Caso from trying again this year. Or, apparently, some traders from taking his second warning seriously. With the Dow trading higher and Apple's shares already down 25% from this year's highs, the stock was stuck in negative territory nearly all day Thursday.

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