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 transportation equipment manufacturer Wabash National (NYSE: WNC) got a big lift today, gaining as much as 14% in intraday trading before finishing the day with a 12.7% gain.

So what: Wabash wowed investors when it released its fourth-quarter earnings after the close of trading yesterday. For the quarter, the company managed $0.11 in earnings per share on $342 million in total revenue. Sales were up 41% from the prior year, while earnings per share increased 57%. Wabash's per-share profit also easily topped the $0.09 that Wall Street analysts were looking for.

Now what: On a longer-term basis, Wabash's success will depend on big-picture issues like continuing to make trailers that customers want to buy while also diversifying outside of that core market. However, for investors looking at quarter-to-quarter performance, the results are largely going to depend on the extent to which the economy continues to improve and businesses are willing to spend more. Last month's employment report was certainly a good sign, but in the wake of the financial meltdown, it's been a very slow, halting process, and I don't expect that that will suddenly change.

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