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 oil and gas explorer Penn Virginia (NYSE: PVA) fell as much as 13.5% before closing down 10% after reporting disappointing second quarter results on Wednesday night.

So what: Both revenue and earnings fell short of expectations. Penn Virginia lost $0.26 after accounting for a variety of adjustments on $73 million in revenue. Analysts had been looking for a $0.25 loss on $74.2 million in sales.

Now what: We've heard this record before. Penn Virginia misses estimates so consistently you could set a clock to it. It's hard to believe that, as a group, the 215 Fools who've rated the stock in Motley Fool CAPS give it four of five stars. How do you rate Penn Virginia? Weigh in using the comments box below.

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Fool contributor Tim Beyers is a member of theMotley Fool Rule Breakers stock-picking team. He didn’t own shares in any of the companies mentioned in this article at the time of publication. Check out Tim'sportfolio holdings andFoolish writings, or connect with him on Google+ or Twitter, where he goes by @milehighfool. You can also get his insightsdelivered directly to your RSS reader.

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