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 printer maker Lexmark International (NYSE: LXK) are flashing warning lights today, sinking as much as 16.8% overnight on tremendous trading volume.

So what: Lexmark's first-quarter results didn't measure up to Wall Street expectations, and neither did the outlook for the coming quarter. Management pointed to competitive pressures and the challenges of refocusing its business on the higher-margin enterprise segment.

Now what: If Lexmark is suffering under competitive pressures, I think it's because the company doesn't execute as crisply as Canon (NYSE: CAJ) and Hewlett-Packard (NYSE: HPQ). Mind you, all three of the printer giants have seen their shares lagging the broader market over the past year, so there might be something to Lexmark's claims. Just keep in mind that HP recently reported that its printer sales grew at a double-digit clip, year over year, while Lexmark's are declining at roughly the same rate.

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Fool contributor Anders Bylund holds no position in any of the companies discussed here. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.