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 SFN Group (NYSE: SFN) popped as high as 10% in intraday trading Thursday as investors applauded the staffing specialist's quarterly results.

So what: Fueled in large part by a 29% revenue surge at its professional services segment, SFN posted adjusted fourth-quarter earnings of $9.4 million, compared with just $3.2 million in the same year-ago period. SFN shares were beaten down badly during the downturn, falling as low as $1.15 in late 2008, but steadily improving industry trends have boosted them to new five-year highs of $11.50.

Now what: I wouldn't be so quick to jump onto SFN at this point. The shares have more than doubled since July and trade at a clear P/E premium to much larger rivals Manpower and Robert Half International. While SFN CEO Roy Krause believes the "longer-term industry dynamics are positive," Mr. Market seems to be pricing in much of that optimism.

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