Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of upscale jewelry retailer Tiffany (NYSE: TIF) sank 12% Tuesday after management cut its full-year earnings guidance.

So what: Tiffany managed to post better-than-expected growth in the first three quarters of 2011, but particularly weak sales in the U.S. and Europe during the holiday season is forcing Mr. Market to sober up a bit. High-end retailers have certainly recovered much faster than other segments over the past couple of years, but Tiffany's profit warning suggests that the trend may no longer be sustainable.

Now what: Management now sees full-year fiscal EPS of $3.60-$3.65, versus its previous view of $3.70-$3.80. "We remain confident of our ability to expand our worldwide presence, to serve the growing global demand for TIFFANY & CO. products and to achieve a solid rate of annual growth in sales and earnings in 2012 despite economic challenges," said CEO Michael Kowalski. However, when you couple today's worrisome guidance with the stock's not-so-low P/E of 17, I wouldn't buy into that optimism just yet.

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