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 mortgage insurer MGIC Investment (NYSE: MTG) jumped more than 10% in intraday trading, as the company reported better-than-expected third-quarter earnings.

So What: Thanks the wave of mortgage defaults washing over the U.S., mortgage insurers such as MGIC have been chalking up huge losses. After reporting a surprise profit last quarter, the company was back in the red this quarter, but its $0.26 per-share loss was not only much better than the $4.17 drubbing a year ago, but also better than the $0.67 loss that analysts expected.

Now What: Shares of the mortgage insurers have been bouncing all over the place lately, most notably thanks to the foreclosure debacle now plaguing banks like Bank of America (NYSE: BAC) and Citigroup (NYSE: C). Shares of MGIC, along with other insurers like Ambac (NYSE: ABK) and PMI Group (NYSE: PMI) were hopping last week, as investors hoped that the foreclosure mess would mean more room for the insurers to put losses back onto the banks. While it's possible that could provide some relief for the group, the real path back to sustainability will depend on tighter underwriting standards -- and getting the rest of the bubble-era junk flushed off the balance sheets.

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