Line chart of the relative proportions of 5 methods of steel production from 1860 to about 2012. From 1860, the Bessemer Thomas method climbs steeply within a decade to be 80% of production, plateaus for a bit more than a decade and then declines to zero by the late 1970s. From 1870, the Siemens-Martin method steadily replaces it, peaking at 80% around 1950 and then declines more sharply to zero around 2012. From about 1920, the electric arc method grows more slowly to about 35% around 2000 and looks to have been in decline since. The direct reduction method arises in the 1970s, accounting for maybe 8% by 2012. Since 1950, the oxygen converter method has grown sharply to almost 70%.