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 private mortgage insurer Radian Group (NYSE: RDN) shed more than 10% in intraday trading, as investors reacted to earnings from competitor PMI Group (NYSE: PMI).

So What: PMI Group's earnings clearly disappointed investors, sending its shares tumbling nearly 20%. Radian Group is set to report its earnings early next week, and investors may be taking PMI's lackluster report as a sign that Radian's results may disappoint as well.

Now What: Fellow private mortgage insurer MGIC Investment (NYSE: MTG) also fell on the news, which was a bit strange, considering that MGIC already reported earnings that came in above expectations. These mortgage insurers are all in pretty bad shape, but those investors still sniffing around Radian might be well advised to wait to freak out until it actually reports its own earnings.

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