Monte Carlo & projections

Why single-number projections mislead, and how probability-based planning works.

7 articles on monte carlo & projections

Monte Carlo retirement planning: what 1,000 lifetimes show that one projection hides

Monte Carlo retirement planning on one frozen retiree: real p50 $1.08M, p10 $0, p90 $5.69M at year 30, 10.4% ruin, versus a 7% deterministic path. 1,000 paths, seed 20260622.

August 29, 2026

Why 90% chance of success is the right goal and 100% is a trap

90% chance of success vs 100%: rigid 3.95% hits 90% on 1,000 paths. 2% still only 99.4%. 100% is not on the grid.

August 28, 2026

Probability of success vs projected balance

Probability of success vs projected balance on 1,000 shared paths: 2% prints 99.4% and $1.89M median; 6% prints 63.0% and $308k.

August 28, 2026

Monte Carlo vs Historical Backtesting in Retirement Plans

Monte Carlo vs historical backtesting: overlapping 40-year tapes are not a probability. Simulation is assumptive and reproducible. Use both.

August 13, 2026

Does Monte Carlo Overstate Retirement Success?

Does Monte Carlo overstate retirement success? Independent draws miss clustered crashes. Ignoring fees and floors will print a kind number. What we do instead.

August 13, 2026

How Many Monte Carlo Simulations Are Enough?

For most retirement plans, 1,000 simulations is enough: an 85% success rate lands within about 2 points, 83% to 87%. At 100 paths it is ±7.

August 12, 2026

Monte Carlo Simulation in Personal Finance: Why Projections Fall Short

Monte Carlo simulation in personal finance: a $4.3M projection landed at the 71st percentile; the median was $2.9M across 5,000 regime-aware lifetimes.

June 22, 2026

Other topics

  • Retirement withdrawals — Safe withdrawal rates, the 4% rule, and flexible vs rigid spending policies.
  • Sequence of returns risk — Why the order of market returns can matter more than the average — especially near retirement.
  • Investing costs — Fee drag, expense ratios, and the lifetime dollar cost of 1%.
  • Investing behavior — Time in the market vs timing the market, and the cost of panic selling.
  • Strategy comparison — Apples-to-apples benchmarks of allocation and spending rules on identical markets.