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 Yingli Green Energy (NYSE: YGE), a Chinese maker of photovoltaic cells for generating solar power, fell more than 13% in early trading and closed off almost that much after upping second-quarter guidance.

So what: In a press release, management told investors to expect a 35% to 37% increase in solar-module shipments. Earlier guidance had called for a "more than 30%" gain.

Now what: What gives? A Wells Fargo analyst sounded caution because Yingli didn't comment on second-half shipments, Reuters reported. So be it. Yingli enters tomorrow trading for one-third the long-term earnings growth analysts expect. Whatever risks remain, they appear to me to be muted by the stock's cheap valuation. Do you agree? Disagree? Weigh in using the comments box below.

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Fool contributorTim Beyers is a member of theMotley Fool Rule Breakers stock-picking team. He didn't own shares in any of the companies mentioned in this article at the time of publication. Check out Tim'sportfolio holdings andFoolish writings, or connect with him on Google+ or Twitter, where he goes by @milehighfool. You can also get his insightsdelivered directly to your RSS reader.

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