Growth & catch-up
Your economy grows through a convergence (catch-up) model: poor nations can sprint, rich frontier nations plateau — so real development, not just size, decides who reaches the top.
How it works
Each quarter the sim measures your GDP-per-capita (perCap = GDP / population, roughly thousands of USD per person) and derives a development level dev = clamp(perCap/55, 0.02, 1.3). A base 'convergence' growth term slides from 1.2 for the poorest down to 0.30 for the developed — the richer you already are, the less headroom remains.
A policy 'efficiency' multiplier (0.5–1.5) then scales that headroom based on tech sector, education and infrastructure budgets, minus penalties for high tax, tax-strain and high inflation. Crucially it is a multiplier, not an additive bonus, so investment can't smash through the convergence ceiling — frontier economies stay near their limit while poor ones naturally decelerate as they get rich.
On top sits the explicit catch-up engine: an institution score (tech + stability + prosperous neighbors) sets your target per-capita as a fraction of the world frontier (top-3 average). The bigger the gap below target, the bigger the catch-up bonus, up to +1.55%/quarter. Everything is smoothed (lerp toward potential at 0.5) and hard-capped by maturity: poor states can hit ~3.4%/q (~14%/yr), developed ones only ~0.58%/q (~2.3%/yr).
Formulas
dev = clamp(perCap / 55, 0.02, 1.3), where perCap = GDP / populationconvergence = lerp(1.2, 0.30, clamp(dev, 0, 1))eff = clamp(1 + (tech−15)×0.012 + (edu−20)×0.008 + (infra−20)×0.005 − max(0, taxRate−25)×0.015 − taxStrain×0.0035 − max(0, inflation−4)×0.03, 0.5, 1.5)targetPC = frontierPC × inst; catchup = clamp(1 − perCap/targetPC, 0, 1) × 1.55 (only if perCap < targetPC)inst = clamp(0.14 + max(0, tech−8)×0.011 + clamp(stability,0,70)×0.0024 + neighborProsperity×0.10, 0.08, 0.65)gdpGrowth = lerp(gdpGrowth, clamp(potential, −6, 6), 0.5) + R&D/leader/project bonuses, capped at lerp(3.4, 0.58, dev)Key numbers
How to play
- ▸As a developing nation, protect stability and raise the tech sector, education and infrastructure — that lifts your institution score and target, unlocking the full +1.55%/q catch-up.
- ▸As a developed nation you're near the ceiling; don't over-tax chasing growth. Focus efficiency levers (education, infra) instead of expecting explosive numbers.
- ▸Prosperous neighbors feed your institution score (border spillover), so a peaceful, thriving region literally raises your growth potential.
- ▸Keep inflation under 4% and taxes under 25% — every point above those directly erodes the efficiency multiplier.