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 credit insurance specialist Radian Group (NYSE: RDN) don't exactly inspire confidence today; prices dropped as much as 13.5% in fairly heavy morning trading.

So what: The entire mortgage-insurance sector is in disarray today as industry peer MGIC Investment (NYSE: MTG) just reported a loss on increased mortgage default claims and lower revenues. MGIC's plunge was even steeper than Radian's, and PMI Group (NYSE: PMI) completed the trifecta of misery with a swoon of 11.8%.

Now what: Look, this industry hasn't been good to investors since 2007 -- mortgage defaults started rising even before that wholesale panic of 2008. Shares of all three of the major credit insurance providers in this market have lost more than 90% of their value since the real trouble began, even if you've reinvested dividends along the way. Radian just reported $1.78 of mortgage-related expenses per dollar of premiums collected, and the rest of the industry can't be doing much better. The light at the end of the tunnel is still dim, shifty, and so very far away.

Interested in more info on Radian Group? Add it to your watchlist.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.