Hong Kong was the Mainland's second largest trading partner (after the US) in 2014. According to China's Customs Statistics, bilateral trade between the Mainland and Hong Kong amounted to US$376 billion (8.7% of the Mainland's total external trade) in 2014. Of which exports from the Chinese Mainland to Hong Kong stood at US$363 billion, making Hong Kong the second largest export market.
The Mainland has been Hong Kong's largest trading partner since 1985. Share of the Mainland in Hong Kong's global trade jumped from 9.3% in 1978 to 50.3% in 2014. The Chinese Mainland was Hong Kong’s largest import source accounting for 47.1% of Hong Kong’s total imports, and the largest export market accounting for 53.9% of
Hong Kong’s total exports in 2014.
Hong Kong's trade with the Chinese Mainland is to a large extent related to outward processing activities. In 2014, 29.3% of Hong Kong's total exports to the Chinese Mainland were related to outward processing activities. Meanwhile, 38% of Hong Kong’s imports from the Mainland and 71.5% of Hong Kong's re-exports of the Mainland origin to all countries were related to outward processing.
Sources : census &statistics department of Hong kong