What the 5,000 simulations are and aren't
Your results come from 5,000 simulated retirements, each built by drawing a real historical year's stock and bond return, independently, for every year of your plan. Give the same plan twice and you'll get the same answer both times.
Each of the 5,000 simulated paths draws its returns from real U.S. market history — the S&P 500's total return and the 10-year Treasury, going back to 1928 — one year at a time, with replacement, blended by your stock/bond mix for that year. Because every year is drawn independently, a single simulation isn't a single historical stretch played back in order; it's a new, randomly assembled sequence built from real years.
The simulation is seeded from your own plan's inputs, so it's deterministic: the same numbers always produce the same 5,000 paths and the same result, whether you check today or next week, on your phone or your laptop.
Not every number you see along the way used the full 5,000. Live previews, while you're still typing, use a smaller, faster sample (as few as 200 paths) to stay responsive — only the final numbers on your dashboard and full results use the complete 5,000.
What this doesn't model
- Consecutive historical sequences — because years are drawn independently, a real multi-year event like a specific bear market isn't preserved as a run the way it actually happened (though its individual bad years still show up, drawn independently, across the 5,000 paths).
- A forecast or prediction — it's a stress test against a wide range of what real markets have actually done, not a guess at what markets will do next.