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 lighting expert Acuity Brands (NYSE: AYI) were dimming noticeably today, as they dropped as much as 11% in intraday trading after the company reported second-quarter results.

So what: The investor reaction to Acuity's numbers was largely a matter of costs. For the quarter, the light specialist showed revenue that was up 10% from the prior year and was ahead of Wall Street analysts' estimates. However, costs rose as well, with cost of goods rising 9%, while operating costs climbed 8%. Excluding one-time items, Acuity notched $0.57 in earnings per share, easily short of analysts' average estimate of $0.62.

Now what: Acuity is still in the process of recovering from the 2008/2009 recession, when both revenue and profits dipped badly. While the company has made considerable progress -- trailing-12-month earnings are up nearly 40% from fiscal 2010 -- investors obviously are realigning their expectations after a softer-than-expected quarter.

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