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 photovoltaic products manufacturer Yingli Green Energy (NYSE: YGE) are whipsawing wildly for a second day in a row following an analyst downgrade. Shares dropped 10% earlier in the trading session but have rallied to be down only 3% at the moment.

So what: Following yesterday's positive comments from Deutsche Bank analyst Vishal Shah that rallied the entire solar suppliers sector, it's not surprising to see Yingli giving back some of its gains. Then again, Lazard Capital downgrading the stock to neutral from a buy is definitely playing a part in today's drop.

Now what: Analyst upgrades and downgrades are great if you happen to be on the right side of the trade, but they are almost always short-term movements that we can ignore. Today's downgrade shouldn't change your investing thesis on Yingli, and it definitely hasn't changed my opinion that investors would be better off waiting out the solar sector's woes on the sidelines.

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