What happened

Shares of aluminum producer Century Aluminum (NASDAQ:CENX) closed the day down 10.8% on Monday -- which was kind of curious. Century Aluminum hasn't published a press release  in more than a month. It didn't report earnings today. It isn't expected to report earnings again, in fact, for another two months.

So what

What's more, in contrast to the big drop we saw in Century Aluminum's stock price last month, the only news item today that would ordinarily have been expected to move Century Aluminum stock was something that one would expect to move the stock up, not down. S&P Global-Platts reports  this morning that across the pond, London Metal Exchange (LME) stocks of aluminum have declined to just 1.15 million metric tons -- roughly half the 2.3 million metric tons reported at the beginning of this year.

Market pundits aren't entirely certain what to make of this development, noting that aluminum stocks may simply have been shifting away from expensive LME warehouses to cheaper warehouses and other countries. At the same time, Russian aluminum producer Rusal forecast earlier this year that aluminum demand would outstrip aluminum supply by approximately 700,000 metric tons in 2017 -- a development that might explain declining stockpiles of aluminum on the LME.

Aluminum rolls on warehouse shelves

This aluminum warehouse looks pretty well stocked -- but the LME isn't. Image source: Getty Images.

Now what

In any case, though, the reason for the declines is not really the point. The point is that if aluminum stockpiles are indeed being depleted, as appears to be the case, then you would expect this to be seen as good news for aluminum producers such as Century Aluminum.

In which case, of course, the nearly 11% decline in Century Aluminum's stock price makes no sense.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.