About Backvest
Backvest backtests real mutual funds and ETFs — not abstract asset classes — and is built around one idea: the most valuable output of a backtest is knowing how much not to trust it.
The honesty principles
When two portfolios differ by less than the noise in the data (a few hundredths of a percent, or the uncertainty from stand-in history), Backvest shows them at the same rank. Most tools rank them anyway — that ranking is fiction.
A search that says “exactly 62% stocks” is overfit. Backvest reports ranges — “55–65% large-cap works about equally well” — because answers that survive small changes are the ones that survive the future.
Every search stress-tests its winners: reshuffle history (bootstrap) and re-pick winners over time (walk-forward). When past champions land mid-pack out of sample — which is typical — Backvest says so on the result.
Funds younger than your test window get history assembled from older share classes or benchmarks. Every splice appears in a methodology table with a confidence grade, and rankings inside that uncertainty render as ties.
Funds that closed or merged aren't in any free dataset, so every screen quietly favors survivors. Backvest can't cure that; it prints the warning wherever it matters instead of pretending.
How the numbers are made
- Monthly total returns (dividends and distributions reinvested) from fund NAV and ETF price histories; mutual-fund returns are already net of fund expenses.
- Backtests simulate real rebalancing (monthly to annual, threshold, or none), contributions and withdrawals, and use time-weighted returns for risk metrics.
- Rolling-window analysis measures every possible start date, so a result that depends on one lucky entry point is visible immediately.
- Searches test every allocation on a grid (up to millions), then stress-test the leaders. Large searches use a disclosed two-stage scan-then-refine method.
- Data quality is graded per fund (A–F); gaps and suspicious jumps block analyses loudly instead of being silently patched.
Data sources & limits
Prices and distributions currently come from public market-data feeds; expense ratios are seed values pending verified filings, and are flagged wherever shown. Fund descriptions link to Morningstar and Yahoo Finance for independent research. Institutional-grade exchange data is on the roadmap.