General Motors reported less than stellar fourth quarter earnings last week, and announced that bonuses paid to its UAW workers will average $4,300. The earnings report disappointed Wall Street as GM shares fell about 4% on the news.

Some media sources attributed the drop in GM’s share price to rising oil prices. Considering that oil prices went down on the day that GM shares fell, this explanation does not hold water. Rather, there are some specific issues relating to the earnings announcement that are causing concern on Wall Street.

Specific items of concern on GM’s fourth quarter earnings breakdown include declining market share in China. Year over year GM market share for China fell from 13.2% to 11.4%. Anyone who has been listening to the hype revolving around GM’s strength in China might be surprised by these numbers. GM CEO, Dan Akerson, has touted China as a bright spot that GM will continue to focus on. Profitability in the region was actually down due to higher costs.

Another area of concern is stagnant sales for GM’s core brand, Chevrolet. Sales for Chevy were flat year over year and new product launch remains weak. Total fourth quarter GM North American market share fell from 19.2% in 2009 to 18.5% in 2010.

One more item worth noting is the fact that much of GM’s quarterly earnings were derived from non-operating income. A large portion of this segment is attributed to a gain from the $45 billion tax credit GM was granted after bankruptcy.

Perhaps the best indicator of how well (or not) GM is doing since its taxpayer funded bailout is its stock performance. Since the time of GM’s IPO, the S&P 500 is up about 10%. GM share price is currently hovering around its IPO price of $33. Shares are down about 5% from where they actually first opened. That is a negative 15% return compared to the broader market. And this during a time when analyst and media coverage was very favorable!

It seems there are many reasons for potential investors in GM to remain cautious, not the least of which is the continued UAW overhang. The fourth quarter saw GM burn through $2.8 billion as $4 billion was contributed to the UAW pension fund. An additional $2 billion of common stock was contributed as well. It is likely that the UAW will continue to expect a large portion of GM’s future profits, IF they exist.