Imagine, for argument's sake, Hong Kong suddenly threw open its doors to the mainland. Life in Hong Kong would undoubtedly be transformed at all levels, in ways both good and bad.
Businesses big and small would be faced with a vastly greater labour pool, allowing for greater competition. The level of skills and services would rise while wages would probably tumble. Property values may rise, boosted by immigration as an economic stimulus. Overall economic efficiency may well improve while the size of the wider economic cake would grow.
Other aspects would not be so rosy, however. Social problems could loom as the city absorbed large numbers of immigrants, putting strains on health, education and social services. Some Hong Kong people would fear a loss of identity amid the tide. Others would struggle to survive, unable to compete with mainlanders willing to work at much lower wages.
In such a scenario, the government would have only limited powers at its disposal to solve the problems. To cope, Hong Kong would have to prioritise its resources, fine-tune its administration and boost all manner of co-operation with the mainland. It would require a sense of fairness based on firm policy principles.
Such a scenario, naturally, would not happen overnight. Over time, however, it is very likely that the borders will grow ever more porous. Hong Kong needs to be setting in place those guiding principles now, helping it to grow and cope in the future.
The long-awaited report of the Taskforce on Population Policy unveiled by Chief Secretary Donald Tsang Yam-kuen last night is Hong Kong's first attempt to grapple with this massive but pressing issue.