Demographics Tool for Micras Worldbuilding

Calculation Methodology

• Age pyramid generation: Uses life-table survival curves with a radix of 100,000. Fertility rate is converted to birth rate assuming a 35-year reproductive span. Population is distributed across standard 5-year age brackets (0-4 through 80+), with age-specific male/female ratios based on differential mortality patterns.
• Development presets: GDP per capita brackets drive correlated defaults for urbanization, literacy, life expectancy, infant mortality, fertility, household size, and agricultural sector share. Five tiers from low-income (<$1,500) to high-income (>$40,000).
• Plausibility engine: Three validation tiers — hard constraints (values outside any observed range), strong warnings (statistically unusual combinations), and soft suggestions (atypical but plausible values). Driven by 9 GDP-demographic correlation sets in data/correlations.json.
• Country presets: 20+ real-world country profiles derived from 2023-2024 data, grouped by region. Used as starting points — all values are editable after loading.

Key Assumptions

• Standard 5-year age brackets with life-table radix of 100,000
• Fertility-to-birth-rate conversion assumes a 35-year reproductive span
• GDP-demographic correlations are cross-sectional (observed patterns), not causal models
• Country presets are approximate — simplified from complex real-world distributions
• Migration modeling is additive to natural growth, not interactive with age structure
• Time dimension projections use linear trend extrapolation, not cohort-component models
• Plausibility ranges are calibrated to observed cross-country variation, not statistical confidence intervals

Data Sources

• World Bank Open Data — GDP per capita, urbanization rates, fertility rates, life expectancy, literacy rates, infant mortality
• CIA World Factbook — Demographic profiles, economic sector breakdowns, country-level statistics
• UNDP Human Development Report — Age structure patterns, development indicators
• Internal correlation data — data/correlations.json contains GDP-demographic correlation ranges with min/max/typical values across 5 income brackets

Limitations

• Single-nation model — no bilateral migration flows or trade dependencies
• Pre-modern and fantasy-technology societies may not fit modern demographic correlations
• Ethnic and religious distributions are entirely user-defined, not generated from correlations
• Time projections are illustrative trend lines, not predictive demographic forecasts