BACKTEST - THE WHOLE BASKET
Portfolio backtesting: backtest a portfolio on 20+ years of adjusted data
Name the holdings and the weights the way you would say them out loud. Agenttrading backtests the whole portfolio against a buy-and-hold benchmark, shades the worst drawdown, and tells you plainly whether the mix earned its complexity.
- 1 THESIS
- 2 EVIDENCE
- 3 BACKTEST
- 4 RISK
- 5 VERDICT
02 EVIDENCE · FUNDAMENTALS
04 RISK · IN PLAIN ENGLISH
Past performance does not guarantee future results. Educational analysis only, not financial advice.
In short
Portfolio backtesting tests a basket of holdings and their weights against historical data, rather than a single ticker, to show how the combination would have behaved through real bull markets, bear markets, and flat stretches. To backtest a portfolio in Agenttrading you describe it in plain English, such as "60% SPY, 30% QQQ, 10% GLD, rebalanced annually", and the bench restates it as an explicit allocation card before running anything. It then tests the mix on 20+ years of split- and dividend-adjusted daily data with dividends reinvested and a 0.1% cost per trade assumed by default, plots the portfolio against a buy-and-hold benchmark, shades the worst peak-to-trough drawdown and prints how long recovery took, and stamps an honest verdict: HELD UP, MIXED, or UNDERPERFORMED. The last one matters most, because a diversified mix that trails a plain index fund after costs is the single most common result in portfolio backtesting, and the bench says so rather than hiding it. That is the difference from Portfolio Visualizer, which is a long configuration form that returns a table and leaves the interpretation entirely to you. Agenttrading starts at $19 per month, requires no code or spreadsheet, executes no trades, and connects to no brokerage. Past performance does not guarantee future results, and this is educational analysis, never personalized advice: the bench shows you what the record says, and you decide what it means.
Past performance does not guarantee future results. For educational and informational purposes only. Not financial advice. Consult a licensed advisor.
WHAT YOU GET - PORTFOLIO BACKTESTING
Portfolio backtesting, run on the bench
The allocation is shown before it runs
Agenttrading restates "60/30/10, rebalanced annually" as an explicit allocation card, tickers, weights, and rebalance cadence, before the test starts. If it misread you, you rephrase and rerun in seconds.
Rebalancing and dividends are modeled, not assumed away
Dividends are reinvested, rebalance cadence is applied on schedule, and the 0.1% default cost per trade is charged every time the portfolio trades. Rebalancing is not free, and the result shows it.
Drawdown read in plain English
The worst peak-to-trough decline is shaded on the chart with its depth, its duration, and how long the recovery took, because the question that actually decides a portfolio is whether you could have held it through the worst stretch.
Honest verdicts, including the boring one
HELD UP, MIXED, or UNDERPERFORMED, stamped against buy-and-hold. The most useful portfolio backtest result is often "your clever mix trailed a plain index fund after costs", and the bench keeps that verdict prominent.
HOW IT WORKS - 4 STEPS
From a sentence to a stamped verdict
Describe the portfolio in plain English
Something like "60% SPY, 30% QQQ, 10% GLD, rebalanced annually" is enough. No spreadsheet, no configuration form, no code.
Confirm the allocation card
The bench shows the tickers, weights, rebalance cadence, and cost assumption it extracted, and waits. Edit anything that does not match what you meant.
Run it across 20+ years
The mix is tested on split- and dividend-adjusted daily data and plotted against buy-and-hold, with the worst drawdown window shaded and every assumption printed.
Read the risks, then the verdict
Drawdown depth, recovery time, concentration, and regime dependence in plain English, then the verdict stamps. Historical, not predictive. You decide.
Past performance does not guarantee future results. For educational and informational purposes only. Not financial advice. Consult a licensed advisor.
On the same bench
A portfolio is a basket of rules, so the stations connect: the backtesting software page explains the plain-English rule engine every test runs on, and historical stock data covers the adjusted 20-year record behind the numbers. The drawdown and concentration read that follows every run is described on investment risk analysis, ETF-weighted mixes get the persona view on ETF backtesting for ETF investors, and if you are configuring forms today the Portfolio Visualizer alternative comparison is the honest read. Step-by-step, the method is laid out in how to backtest a portfolio.
QUESTIONS - ASKED AND ANSWERED
Portfolio backtesting: the common questions
What is portfolio backtesting?
Portfolio backtesting tests a basket of holdings and their weights against historical market data to show how the combination would have behaved over time. Unlike backtesting a single ticker, it captures how the holdings interact: whether they fell together in a crash, whether rebalancing added anything, and whether the mix beat simply holding a broad index fund after costs.
How do you backtest a portfolio?
Define the exact holdings, weights, and rebalance cadence; use daily prices adjusted for splits and dividends across 20+ years so the mix faces at least two bear markets; charge realistic trading costs, roughly 0.1% per trade, on every rebalance; run the allocation mechanically over the full period; then compare the result against a buy-and-hold benchmark and read the maximum drawdown, not just the return.
How accurate is portfolio backtesting?
A portfolio backtest is an accurate record of what a rule would have done on the data given, and nothing more. It is not a forecast. Its accuracy degrades with short samples, unadjusted prices, ignored trading costs, survivorship bias in the ticker list, and overfitting from testing many allocations and keeping the prettiest. Treat a backtest as evidence about the past, weighted by how honestly it was run.
How many years of data do you need to backtest a portfolio?
Use at least 20 years. A shorter window can miss every serious bear market and produce a portfolio that looks resilient only because it was never tested. Twenty-plus years of adjusted daily data covers the dot-com unwind, 2008, and 2020, which is the minimum for judging whether an allocation survives regimes rather than one favorable decade.
Can you backtest an ETF portfolio?
Yes. ETF portfolios are the most common thing tested on the bench, because weights and rebalancing dominate the outcome. Name the ETFs and weights in plain English, set a rebalance cadence, and the test runs on adjusted daily data with dividends reinvested and costs charged on every rebalance.
Past performance does not guarantee future results. For educational and informational purposes only. Not financial advice. Consult a licensed advisor.
Your next idea deserves a verdict, not a hunch.
Bring a thesis or a ticker. Agenttrading restates the rule, shows the evidence, runs 20+ years of history, and stamps an honest verdict. You decide.
Past performance does not guarantee future results. For educational and informational purposes only. Not financial advice. Consult a licensed advisor.