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 auto parts dealer Dorman Products (Nasdaq: DORM) fell 10% today on news of insider sales.

So what: CEO Richard Berman and his brother -- president and director Steve Berman -- will sell up to 250,000 shares each. CFO Mathias Barton will also sell 25,000 shares, so insiders aren't giving the market a good signal today.

Now what: Insiders selling can be a bad signal for the future performance of a stock, and when everyone is running for the hills I get a little worried. Both Bermans are selling a big portion of their shares, so they must not think the company can keep crushing estimates like it has for the last year. At the risk of going along with a panic sell, I don't see this as a good sign for investors.

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