South Korea’s total dependency ratio, measuring dependents relative to 100 working-age people, is projected to rise from the lowest among OECD members in 2026 to the highest by 2048. OECD population projections show the ratio increasing from 45.4 people in 2026 to 117.3 by 2070, as low birth rates and rapid aging expand the socioeconomic burden on the labor force. South Korea is expected to overtake Greece in 2048, when its ratio reaches 90.2 compared with Greece’s 90.1, and its 2070 level would represent a 2.6-fold increase, the largest rise among OECD nations. Its elderly dependency ratio is also projected to surpass Japan’s by 2045, reaching 68.4 compared with Japan’s 67.6, before rising to 103.3 by 2070. Mandatory spending on elderly welfare programs is projected to reach 33.114 trillion Korean won in 2030, up 28.7% from 25.7227 trillion won in 2026, while total mandatory welfare expenditures are expected to reach 256.6615 trillion won, a 30.8% increase from previous levels.