Shanghai is one of the main industrial centers of China, playing a key role in China's heavy industries. A large number of industrial zones, including Shanghai Hongqiao Economic and Technological Development Zone, Jinqiao Export Economic Processing Zone, Minhang Economic and Technological Development Zone, and Shanghai Caohejing High-Tech Development Zone, are backbones of Shanghai's secondary industry. Heavy industries accounted for 78% of the gross industrial output in 2009. China's largest steelmaker Baosteel Group, China's largest shipbuilding base -- Hudong-Zhonghua Shipbuilding Group, and the Jiangnan Shipyard, one of China's oldest shipbuilders are all located in Shanghai.[74][75] Auto manufacture is another important industry. The Shanghai-based SAIC Motor is one of the three largest automotive corporations in China, and has strategic partnerships with Volkswagen and General Motors.[76]