Simulator questions and answers
Which tool should I use?
Simulator tests Single, Compare, and Portfolio scenarios. The homepage's Quant Lab tests factor-selection rules using a separate dataset. TSP/401(k) models payroll contributions. The studies provide fixed, reproducible examples.
Do public tools require an account?
No. Public calculations run in your browser and market-data requests go to our API. A separate private portfolio plan requires its operator's PIN. See Privacy for its session cookie and request logging.
Why are both zero deposits rejected?
There would be no investment to simulate. To measure endpoint growth, use $10,000 initial and $0 monthly. Divide ending value by $10,000 for the growth multiple. For periodic saving, use $0 initial and a positive monthly amount.
When is the first monthly contribution made?
At the first selected observation, in addition to any initial deposit. Contributions also occur on the final observation. Twelve observations therefore include twelve deposits and eleven intervals of price change.
Are prices month-end and dividend-adjusted?
The main simulator uses the first available trading-day observation in each month. Stocks and ETFs use adjusted-close data that can reflect dividends and splits; the S&P 500 series is a price index without reinvested dividends. Quant Lab has a separate month-end dataset. See methodology before comparing them.
What does the model omit?
Taxes, transaction costs, spreads, inflation, and cash interest are excluded from the main simulator. Fractional units are allowed. Monthly samples can miss interim drawdowns. Current membership and share counts bias historical Quant Lab tests. A backtest is not a forecast.
How fresh are the data?
Check the last returned observation and available dates in the specific tool. Different pipelines refresh separately, and a failed update can leave stale data. The studies intentionally use frozen snapshots; their results do not automatically change when live prices update.
How can I verify or report a result?
Save the symbol, date range, deposits, weights, and rebalancing setting. Inspect the price API or download a study's CSV and calculation script. Contact us with the URL, inputs, expected result, and source of the discrepancy.