July 1, 2017, will mark the 20th anniversary of Hong Kong's reunification with the motherland. It comes at a moment when Chinese leaders are increasingly promoting Hong Kong's unique role in advancing the country's economic development.

Two months ago, Premier Li Keqiang described China's intention to deepen economic cooperation across the Guangdong-Hong Kong-Macao Bay Area - which Hong Kong analysts call the Pearl River Delta region - in order to reinforce its role as a major driver of sustainable development. The region comprises Guangdong's nine key cities - including Guangzhou, Foshan and Shenzhen - plus Hong Kong and Macao. Last year, the PRD region's population stood at 68 million, and its GDP was $1.3 trillion.

The PRD region is the southern pillar of the three Chinese coastal growth clusters. In the middle is the Yangtze River Delta region, which includes Shanghai and has a population of 130 million and GDP of $2 trillion. To the north is the Beijing-Tianjin-Bohai corridor, covering 10 key cities; it has a population of 100 million and GDP of $1.3 trillion. Taken together, these three clusters account for 21 percent of China's population and just under 40 percent of its GDP.