How Population Shapes Growth: The Economics of an Ageing World

Economic growth, in its simplest textbook formulation, comes from some combination of more workers, more capital, and higher productivity. Demographic change operates most directly on the first of these: a shrinking working-age population, all else equal, shrinks the labour input into the growth equation, and no amount of productivity improvement can fully offset a labour force that is actively contracting in absolute headcount rather than merely growing more slowly.

The mechanism runs through the dependency ratio — the number of children and retirees relative to working-age adults. As birth rates fall below replacement level (roughly 2.1 children per woman) and life expectancy rises, dependency ratios climb steadily: fewer workers must support more retirees, both through direct family support and through public pension and healthcare systems funded by current tax revenue. The OECD's projection of an 8% working-age population decline by 2060, paired with a 3-percentage-point rise in pension and health spending as a share of GDP, illustrates both sides of this mechanism operating simultaneously — a shrinking tax base combined with rising age-related spending obligations, a fiscal squeeze that compounds over decades rather than arriving as a single shock.

Japan remains the most-studied real-world case of advanced demographic ageing, having already experienced decades of a shrinking working-age population alongside persistently low growth and, for extended periods, deflationary pressure. South Korea and increasingly China are following similar trajectories at a faster pace than Japan experienced, complicated in China's case by the lingering demographic effects of its one-child policy (1980-2015), which compressed an entire generation's birth cohort and is now working its way through the population pyramid as that generation approaches retirement age with comparatively few working-age children to support it.

Europe faces a related but distinct challenge: absent substantial immigration, the region is projected to face a shortfall of 44 million workers by 2050, a gap current birth rates cannot close within any policy-relevant timeframe, since a shift in fertility today would take roughly two decades to translate into new labour force entrants. This has made immigration policy an increasingly central economic — not just social or political — variable in European growth projections.

Not all economies face this challenge simultaneously, and the divergence matters enormously for global growth patterns. India, with a median age still in the high twenties and a working-age population still expanding, sits in a very different position — provided it can generate enough productive employment to absorb its expanding labour force, a genuine ‘demographic dividend’ that already-ageing economies like Japan, Germany, and increasingly China have already spent and cannot recover. Much of sub-Saharan Africa retains an even younger population profile, representing perhaps the largest remaining demographic dividend opportunity globally over the coming decades.

The policy responses available to ageing economies are limited and each carries trade-offs: raising retirement ages, increasing immigration, boosting productivity through capital deepening and automation, and pro-natalist family policy. No advanced economy has yet found a combination of these levers sufficient to fully reverse the growth-dampening arithmetic of a shrinking, ageing workforce — which is why demographic economics has moved from a specialist academic subfield to a mainstream macroeconomic concern occupying central bank and finance ministry forecasts worldwide.