Demography + Economics Lab
Change demographic and economic assumptions and watch population, GDP per capita, labor force, and fiscal pressure evolve together.
Why this feels like math magic 🖖
The key is decomposition: the same final GDP path can come from very different drivers. This lab separates demography, labor, productivity, and fiscal load so tradeoffs become visible. Population dynamics compound slowly but dominate over 45 years — a 0.3% annual net migration rate doubles the effect of a large productivity boost.
Total output versus output per person 🖖
This lab always tracks GDP per capita, not just headline GDP. Output is produced only by workers, yet every resident shares it — so the total and the per-person figure can drift in opposite directions. A country whose population outpaces its economy can look richer in total while each person grows poorer. Watch the two curves split whenever the working-age share shrinks: that gap is what living standards actually feel.
A shrinking nation has a half-life 🖖
The population step P_{t+1} = P_t(1 + b − d + m) is pure geometric growth — the same equation behind compound interest and radioactive decay. When births plus migration fall short of deaths, the net rate turns negative and population decays exponentially, half-life and all. A country contracting 1% per year has a population half-life near 70 years (the rule of 70) — the demographic twin of an isotope's decay curve.