Shenyang is an important industrial center in China and is the core city of Shen Yang Economic Zone, a New Special Reform Zone. It has been focused on heavy industry, particularly aerospace, machine tools, heavy equipment and defence, and recently on software, Automotive and electronics. The heavy industry started in the 1920s and was well developed before the second world war. During the first five-year plan (1951–1956) many factories were built in Tiexi district. At its peak in the 1970s, Shen Yang was one of the top three industrial centers in China alongside Shanghai and Tianjin, and was at one time being considered for upgrading to a direct-controlled municipality. However, as the planned economy fell out of favor after the 1980s, the heavy industry had declined gradually and the city became a rust belt city, with hundreds of thousands of people laid off from bankrupted state-owned factories. However, the economy of the city has revived significantly in recent years, thanks to the central government's "Revitalize Northeast China" campaign and the rapid development of software and auto manufacture industries. Investment subsidies are granted to multinational corporations (MNCs) that set up offices or headquarters in Shen Yang.