Every adult in the economy

One dot per living adult, positioned by age and net worth.

Net worth by percentile

Log scale. Bands show where each slice of the population sits.

Top decile Middle Bottom decile Median

Share of all wealth

How the total pie is divided between groups.

Top 1% Next 9% Middle 40% Bottom 50%

How the model works

  • Each month an adult earns their income and spends a fixed baseline plus a slice of anything above it (lifestyle creep). Whatever is left over is split between invested assets and idle cash.
  • Investments earn a market return each month, drawn around the annual rate with the chosen volatility. Everyone shares the same market swing, then adds their own luck on top, and portfolios above the median earn a small premium on each tenfold of size. Those last two are what let a head start compound instead of washing out within a lifetime. Idle cash earns nothing. Negative balances accrue debt interest but stop at the borrowing limit — past it the shortfall is assumed to be met by a safety net rather than piling up as unpayable debt.
  • Retirement stops income but not spending, so wealth is drawn down: cash first, then assets.
  • Couples form when people reach child-bearing age and have their children together, so every child has two parents and inherits from two estates. Who pairs with whom is set by the "like marries like" dial, scored on income and wealth. Each adult still earns and spends on their own account; household sharing is not modelled.
  • Children start with nothing and only earn from the working age onwards. Their income is drawn partly from the midpoint of their parents' (income inheritance) and partly at random. Childhood costs are folded into the baseline expenditure rather than modelled separately.
  • At death a share of the estate passes to living children in equal parts — so with two children per couple, a child inherits roughly one parent's worth, and larger families dilute it. The remainder is either redistributed equally across all living adults or leaves the economy, depending on the redistribution setting. Debts die with the person.
  • Births are spread over a 15-year window per parent and steered so the adult population settles near its target: enough adults have children to replace the generation one-for-one. The family-size setting decides how many each of those parents has, which is what determines how many ways an estate gets split. Demographic waves from the opening cohort take a couple of generations to damp out.
  • All money is in constant, inflation-adjusted units, so the return rate is a real return. Over centuries even a modest real return compounds to very large numbers — the log axes and the share-of-wealth chart are the readable views at that point.
  • The Gini coefficient and wealth shares treat negative net worth as zero.