For the second time in a week, a government unemployment report is sowing confusion—and may not be as positive as the markets think.

First it was last Friday's August payrolls report, which showed an unexpectedly large drop in the unemployment rate, that spurred confusion (and conspiracy theories). Now, a sharp drop in the pace of new jobless claims has also left people scratching their heads.

The Labor Department on Thursday said the number of people filing jobless claims last week dropped by a seasonally adjusted 30,000—a pretty sharp decline, and one that left the total number of filings at a four-year low of 339,000.

Financial markets immediately rallied on the news. (Read more: Stocks Rise After Jobless Claims Hit 4-Year Low.)

While the government didn’t note any unusual factors in the release itself, a Labor Department official did tell news agencies covering the release about a quirk which partly accounted for the larger-than-expected drop.

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