Population aging is the defining demographic challenge for advanced economies. The combination of increased longevity (people living longer) and decreased fertility (fewer children being born) is creating societies where the ratio of working-age adults to retirees is declining rapidly. This ratio, known as the old-age dependency ratio, has profound implications for economic growth, fiscal sustainability, and social cohesion.
Japan is the world's most advanced case study in aging. Over 29% of its population is aged 65+, adult diapers outsell baby diapers, and entire towns are being abandoned as young people migrate to cities. Japan's response has included robotics investment, extending working life (many Japanese work into their 70s), and very gradually opening to immigration. These measures have slowed but not reversed the economic impact.
Europe's aging is more geographically varied. Northern European countries (Sweden, UK, France) have maintained relatively higher fertility rates and attracted immigration, moderating the aging trend. Southern and Eastern Europe face sharper challenges: Italy's fertility rate of 1.2, combined with emigration of young workers, means its working-age population is shrinking rapidly. Germany has partially offset its low fertility through large-scale immigration.
The fiscal arithmetic is stark. Pension systems designed when there were 5 workers per retiree must now function with 2-3 workers per retiree, heading toward 1.5. This requires some combination of later retirement, reduced benefits, higher taxes, or more immigration. Every option is politically difficult, and countries that delay reform face larger adjustments later.