demographic revolution
Refers to a major shift in population structure, such as the demographic transition from high birth/death rates to low ones, or other transformative population changes.
The demographic revolution has a major impact on society and the economy.
人口転換 specifically refers to the demographic transition model (shift from high to low birth/death rates), while 人口革命 is a broader term for any revolutionary population change.
Compound of 人口 (population) and 革命 (revolution). The term is a direct translation of the English 'demographic revolution'.