There's never a shortage of losers in the stock market. Let's take a closer look at five of this past week's biggest sinkers.


Dec. 20

Weekly Loss

Tower Group International (NASDAQ:TWGP)






Winnebago (NYSE:WGO)



Rockwell Medical (NASDAQ:RMTI)



Rite Aid (NYSE:RAD)



Source: Barron's.

Let's start with Tower Group. The insurer plunged after reporting a reserve shortfall. Naturally, this is a pretty big deal when you're an insurer, and Tower Group isn't in the best financial shape to be adding as much as $105 million to its reserves. 

Gogo shares lost some serious altitude after an early private-equity investor distributed its 27.6 million shares to its limited partners. The move naturally doesn't have any bearing on the fundamentals of the fast-growing provider of in-flight Wi-Fi connectivity, but the likely profit-taking by the limited partners could pressure the shares in the near term. 

Winnebago shifted into reverse after the RV maker delivered poorly received quarterly results. Earnings drove past Wall Street's profit targets, but the 15% uptick in sales fell short of the 20% that analysts were forecasting. 

Rockwell Medical called in sick after Brean Capital issued a "sell" rating on the anemia-tackling biotech. The analyst thinks the FDA will reject Rockwell's continuous dialysis session maintenance treatment, setting a $4 price target. A rival analyst at Summer Street Research Partners issued a more upbeat counter to the treatment's prospects, but the market sided with the bear.

Finally we have Rite Aid fumbling its latest prescription. The drugstore operator posted quarterly results that were in line with expectations but followed that up with a disappointing outlook. Rite Aid sees a profit of $0.17 to $0.23 a share for the entire year, implying that its holiday quarter will fall well short of expectations.

Longtime Fool contributor Rick Munarriz and The Motley Fool have no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.