The industrialization of China refers to the process of China undergoing various stages of industrialization. The focus is on the period after the establishment of the People's Republic of China where China experienced its most notable growths in industrialization. Although Chinese industrialization is largely defined by its 20th-century campaigns, China has a long history that contextualizes the proto-industrial efforts, and explains the reasons for delay of industrialization in comparison to Western countries. In 1952, 83 percent of the Chinese workforce were employed in agriculture. The figure remained high, but was declining steadily, throughout the early phase of industrialization between the 1960s and 1990s. In view of the rapid population growth, however, this amounted to a rapid growth of the industrial sector in absolute terms, of up to 11 percent per year during the period. By 1977, the fraction of the workforce employed in agriculture had fallen to about 77 percent, and by 2012, to 33 percent. Historical precursors of industrialization In the State of Wu of China, steel was first made, preceding the Europeans by over 1,000 years. The Song dynasty saw intensive industry in steel production, and coal mining. No other premodern state advanced nearly as close to starting an industrial revolution as the Southern Song. The lack of potential customers for products manufactured by machines instead of artisans was due to the absence of a "middle class" in Song China which was the reason for the failure to industrialize. Western historians debate whether bloomery-based ironworking ever spread to China from the Middle East. Around 500 BC, however, metalworkers in the southern state of Wu developed an iron smelting technology that would not be practiced in Europe until late medieval times. In Wu, iron smelters achieved a temperature of 1130 °C, hot enough to be considered a blast furnace which could create cast iron. At this temperature, iron combines with 4.3% carbon and melts. As a liquid, iron can be cast into molds, a method far less laborious than individually forging each piece of iron from a bloom. Cast iron is rather brittle and unsuitable for striking implements. It can, however, be decarburized to steel or wrought iron by heating it in air for several days. In China, these ironworking methods spread northward, and by 300 BC, iron was the material of choice throughout China for most tools and weapons. A mass grave in Hebei province, dated to the