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 American Capital (Nasdaq: ACAS) soared as much as 11% on heavy volume when the investment firm reported strong fourth-quarter results and a positive 2011 outlook.

So what: Not long ago, American Capital was considered a candidate for bankruptcy. No longer. Last night, the firm, which provides debt financing to growing middle market companies, reported $0.19 in per-share earnings on $143 million in operating income. Analysts were expecting $0.17 and $140.86 million, respectively.

Now what: Many Fools saw this coming. So did insiders. CEO Malon Wilkus had been a buyer of his company's shares in September, when they were still trading for $5.88 a share. (Insiders still own 2.09% of the business despite an increase in planned 10b5-1 sales since December.)

The stock is less of a bargain today but still trades for 12% below American Capital's $10.71 in net asset value per share. I'm a buyer right up to the point when the share price exceeds NAV, which could be later this year.

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