Blog
Notes on retirement planning, financial modeling, and building retplan.
A century of market returns, bundled into your browser
July 27, 2026
How retplan backtests your plan against 1928-2023 market history - with the whole dataset shipped as part of the site, so nothing you enter ever leaves the page.
What the 4% rule actually says
July 25, 2026
The most-quoted number in retirement planning is a narrow claim about a specific dataset. Where it comes from, what it quietly assumes, and how to test it against your own plan instead.
Monte Carlo or historical backtest?
July 24, 2026
retplan stresses your retirement plan two ways - thousands of randomized futures, or every stretch of real market history since 1928. What each method catches, and what each one misses.
Introducing retplan
July 22, 2026
Why we built a retirement planner that runs entirely in your browser - and what's inside.