Hong Kong is increasingly being urged to develop a comprehensive population policy. Academics, policymakers and business leaders warn that rapid ageing, low fertility and a shrinking labour force threaten the city’s competitiveness, and call for more decisive government intervention.

Most such calls converge around two familiar strategies: encouraging Hong Kong women to have more children and attracting more immigrants. Both approaches assume Hong Kong must resolve its demographic challenges largely within its boundaries.

That assumption reflects a city state logic. Yet Hong Kong today functions more like a core city within a vast mega-metropolitan region. Population policy built on the former mindset risks misdiagnosing the problem.

Hong Kong’s low fertility is no longer primarily a behavioural issue but increasingly a structural constraint. According to government statistics, Hongkongers’ median age rose to 49.4 years last year, with nearly a quarter of the population aged 65 or older. Most women are 40 or older – past the typical age for childbearing.

More generous incentives or family-friendly policies can raise fertility only at the margins when the pool of potential mothers is shrinking – a significant rebound in babies is unrealistic. But this is not a failure of policy ambition or political will. When a city has aged as far as Hong Kong has, a birth-centred population policy can at best slow the decline; it cannot reverse it.

Immigration is often presented as a more practical alternative. Hong Kong has long depended on talent inflows and remaining open to skills and labour is widely seen as essential. Yet much of the debate collapses two very different processes into one: cross-border immigration and intra-metropolitan relocation.