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 media research firm Arbitron (NYSE: ARB) are surging 16% today after the company renewed a deal with Clear Channel Radio, provided fiscal 2011 earnings guidance, and received an upgrade from JPMorgan.

So what: Arbitron satisfied analysts by providing forward earnings guidance that was at the high end of Wall Street's range. The Street had been looking for revenue growth of 6% with $1.90 per share in 2011 -- Arbitron's guidance was for 6% to 8% revenue growth with an earnings-per-share range of $1.90 to $2.05. Arbitron also locked up its largest customer, Clear Channel Radio, to a long-term contract.

Now what: Although we have three pieces of bullish information here, locking up its largest customer to a long-term contract seems like the real catalyst for the jump. Clear Channel Radio provided nearly one-fifth of Arbitron's total 2009 revenue, so locking it up for many years to come takes some of the bottom-line worry off the table. Arbitron's 2011 guidance beat might seem trivial since it was within the range analysts had been looking for, but given their healthy return on equity and lower forward price to earnings relative to the marketing services sector, this guidance boost singles them out as potentially the company to own in this sector.

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Fool contributor Sean Williams does not own shares in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong.

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