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: For the second time in three days, shares of MetroPCS (NYSE: PCS) slumped more than 10% in early trading and are down nearly that much as I write this. Investors just don't believe in the company enough to defy a broad market decline.

So what: Economic uncertainty has torched most stocks today, but MetroPCS is down more than three times the market's 3% pullback. Sellers seem to think the year's worth of growth that preceded the second quarter is now gone, never to return.

Now what: Does this mean AT&T (NYSE: T) and Verizon (NYSE: VZ) are the new old kings of telecom? For the time being, yes. They're the only two carriers with access to the iPhone, and that seems to be making all the difference. Do you agree? Disagree? Weigh in using the comments box below.

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Fool contributor Tim Beyers is a member of the Motley 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's portfolio holdings and Foolish writings, or connect with him on Google+ or Twitter, where he goes by @milehighfool. You can also get his insights delivered directly to your RSS reader.

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