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 coal miner Peabody Energy (NYSE: BTU) fell 11% today after the company released earnings.

So what: During the second quarter, revenue rose slightly to $2.0 billion, just short of the $2.06 billion analysts had expected. On the bottom line, results were even worse, with net income falling 28% to $204.7 million. Excluding special items, earnings per share were $0.51, just $0.02 below estimates, but in the third quarter, management expects earnings per share of $0.20 to $0.45, well below the current $0.65 estimate.

Now what: Peabody is the last of the coal companies to report a significant profit, but even that is evaporating. Coal stocks have been crushed all year on falling demand, and Patriot Coal's bankruptcy earlier this month was a sign of things to come for some in the industry. Peabody is nowhere near that fate right now, but with trends heading in the wrong direction it looks like a value trap, and I certainly wouldn't be a buyer today.

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