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: Even after a boffo Christmas for most retailers, shares of action-sports specialist Zumiez (Nasdaq: ZUMZ) have dropped more than 10% in response to its reported 9.2% growth in same-store sales.

So what: Wait, since when is 9.2% growth a bad thing? Traditionally, retailers like Zumiez tip from loss to profit for the year on "Black Friday," with further profits rolling in over the weeks between Thanksgiving and Christmas. As strong as its same-store sales growth was, Zumiez still missed consensus estimates of 11.5% growth, imperiling its profit estimates for the quarter.

Now what: Oppenheimer tells us that along with American Eagle (NYSE: AEO) and Abercrombie & Fitch (NYSE: ANF), Zumiez was one of the "good" retailers last month, resisting the urge to undercut planned sales prices with even deeper promotional discounts. That margin-bolstering discipline may have cost the company market share, as retailers such as Aeropostale (NYSE: ARO) stole away sales with a greater willingness to mark down their wares.

Zumiez costs a pricey 41 times earnings, while Aeropostale fetches just 10 times. That's a significant discount to the 14% long-term growth Wall Street expects from the latter. The trade here seems kinda obvious to me.

Want to keep closer track of Zumiez's ups and downs? Add it to your watchlist.

Zumiez is a Motley Fool Big Short short-sale pick, and The Fool owns shares of Aeropostale. Fool contributor Rich Smith, however, owns none of the above. The Motley Fool has a disclosure policy.

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