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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