Though the fourth-quarter results for Calamos Asset Management (Nasdaq: CLMS) beat analysts' estimates, it still wasn't a quarter -- or year -- to write home about.

For the quarter, Calamos posted revenue of $125 million, up 2% from the fourth quarter of 2006. Earnings per share grew a somewhat faster 11% and came in at $0.42. For the full year, revenue decreased 2% while earnings per share were down 16%. The company did have a few large expenses during the year that it considers to be one-time in nature -- netting out those, EPS declined just 6%.

As might be expected from the results, assets under management were likewise lackluster. On a sequential basis, AUM fell 1% as $59 million flowed out of funds and $479 million was lost in market depreciation. For the full year, AUM increased $1.5 billion, thanks to strong appreciation of $5.1 billion. The strong performance couldn't keep investors from yanking money, though, and the company saw net redemptions of $3.6 billion during the year.

The story of Calamos is really one of over-reliance on a successful but volatile fund. Calamos' growth fund -- a Morningstar four-star fund that has returned almost 15% annually over the past five years -- currently holds over $16 billion of the company's total $46 billion under management.

The upshot of course is that the fund has been very successful. But what are the characteristics of the typical growth investor? That's right: fickle and ready to pull money out when performance starts to lag. Though the growth fund has been a great performer over time, performance hasn't come in a straight line. For example, though it outperformed the S&P by nearly 18% in 2007, it sorely underperformed by 14% in 2006. And thus far, 2008 hasn't been particularly kind to growth stocks. Major Calamos Growth holdings like Apple (Nasdaq: AAPL), Google (Nasdaq: GOOG), and Garmin (Nasdaq: GRMN) have been clobbered in January, and the fund overall is down 13% versus the S&P's 6% drop.

Management hasn't missed the fact that it needs to diversify, but it's tough to bring funds up to a size that would start balancing out the growth fund overnight. Over the past few years, Calamos has added a fund of funds that combines three of Calamos' funds, an international growth fund, and a blue chip fund. More recently, it's added a global equity fund and a bond fund. With over $500 million under management, the international growth fund is the largest of these, and most of them are still sub-$100 million funds.

While there's certainly a compelling story here, given the proven success of Calamos' growth fund, it's hard to get too excited when competitors like T. Rowe Price (Nasdaq: TROW) and Janus (NYSE: JNS) have been delivering such great results.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. The Fool's disclosure policy has never once been caught with its pants down. Of course, it doesn't actually wear pants ...