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 aluminum producer Century Aluminum (Nasdaq: CENX) were getting the heave-ho from investors today and shed as much as 16% in intraday trading.

So what: Century's first quarter showed definite progress versus the first quarter of last year. Revenue for the quarter was up 14% to $326 million, while earnings per share jumped from $0.06 to $0.25. However, excluding a one-time charge to cost of sales in 2010, last year's earnings per share would have been $0.23. One-time charges during the first quarter of this year were largely offset by one-time benefits. Shipments fell slightly from a year ago, sliding from 144,677 tonnes to 144,178 tonnes.

Now what: Both revenue and earnings per share for the quarter missed Wall Street estimates, and that likely accounts for the market's reaction. The drop in shipments may also be playing to the downside. The weakness there came largely from toll shipments, which fell 6%. Direct shipments rose 5%. Management expressed cautious optimism about the road ahead and said that its Hawesville facility -- which cut production during the downturn -- will be back to full production by the third quarter. For a cyclical company like Century, though, much will depend on whether the economy can continue picking up steam.

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