Coal mining in Liaoyuan started in late Qing dynasty and continued to be the most important industry for more than 100 years. During the Japanese occupation from 1931 to 1945, Liaoyuan was the second largest coal-mining center of Manchukuo, preceded only by Fushun. This city continued to produce approximately 3 million tons of coal every year till the mid 1990s, when the exhaustion of coal resource brought the economy of this city to a standstill. The city succeeded in transforming its economic structure from a mining oriented one to a light manufacturing oriented one. At present, the city is the largest cotton-sock manufacturing center in China. Furthermore, the aluminum shell of Apple Macbook Pro is also manufactured in this city. Liaoyuan has a GDP of RMB 50 billion in 2011, rising 15.6% year on year.