For the third year running, ArcelorMittal SA claimed the title of the world's largest steelmaker. The Luxembourg-based company's raw steel output of 103.3 million tonnes—although down more than 11 percent from 2007—was nearly triple that of its nearest rival, Japan's Nippon Steel Corp.

Although there was some shuffling of the order at the top of the rankings, with China's Baosteel Group Corp. Ltd. moving up two slots to switch places with Japan's JFE Steel Corp., the top five steelmakers remained the same as the previous year. But that continuity belies what was one of the most dramatic years in the history of the steel industry.

Many of the world's steel producers reported in their 2008 results that the first nine months of the year were among the best in their history, while the fourth quarter was among the worst. And following the massive downturn in demand and prices that began in September, 2008 is likely to be remembered as the year the bubble burst on the steel bull market.

One indication of the change is the number of mills that reported a drop in output last year, including two of the top 10 producers. While in recent years almost every steelmaker on the globe was expanding, last year's collapse in demand helped push a number of mills into cutbacks—a pattern that is being repeated in 2009.

The uncertainty over the extent of the global...