Population-Based Systems Models for National Planning: A Proposal for Country-Owned Demographic Systems Infrastructure

Countries face interconnected policy challenges: population aging, fertility change, migration, urbanization, labor transitions, food and water security, climate risk, health-system demand, school planning, housing pressure, consumption planning, and spatial inequality. Yet planning evidence is often fragmented across ministries, statistical offices, surveys, administrative systems, research projects, and dashboards. This paper proposes the Population-Based Systems Model, or PopSyM, as a country-owned analytical infrastructure that places population dynamics at the center of integrated policy planning. PopSyM begins with a demographic spine by age, sex, location, year, and scenario, then links that spine to modules for health, education, food, labor, housing, social protection, environment, and local infrastructure. Its purpose is not projection for its own sake, but the measurement and improvement of population well-being: longer and healthier lives, adequate material conditions, skills, meaningful work, security, dignity, and country-specific dimensions of a good life. Nepal is used as a motivating example, but the proposed architecture is general. The paper argues that the population should be treated not only as a denominator for indicators but also as the organizing framework through which countries understand future demand, vulnerability, consumption needs, policy trade-offs, and feedback between people and systems.