Assumptions
Assumptions covers the two numbers that shape every projection regardless of which section you've opened: your assumed inflation rate, and your stock/bond mix before and after retirement.
Inflation (2.5% by default) is removed from each year's market return before it compounds — see "Why everything is in today's dollars" for why that keeps every number in today's money.
The stock/bond mix is two flat numbers you set yourself — 70% stocks before retirement, 40% after, by default — held flat within each phase. It doesn't taper further with age the way some target-date funds do, and it doesn't automatically de-risk over time.
A "safe-income floor" suggestion shows what stock/bond split would cover your portfolio-funded essential spending using a simplified bond-yield assumption, separate from the engine's own historical return data — it's a suggestion you can apply with one click, not a rule.
A few assumptions shown here are locked previews, not editable yet: custom return assumptions instead of the historical model, separate education/healthcare inflation rates, and a Social Security benefit haircut. These are planned Plus features, not built.
What this doesn't model
- Custom market-return assumptions — the engine always uses the historical 1928–2025 bootstrap.
- Separate inflation rates for college or healthcare — one flat rate applies everywhere.
- A Social Security benefit reduction — full benefits are assumed to be paid.