FAQ
Frequently asked questions
The questions we hear most often. If yours isn't here, send it our way through Contact.
Is this investment advice?
No. PastFi is an analytical tool that uses historical data to show how the same money would have fared across different assets. It doesn't guarantee future returns or recommend any particular asset.
Can I change the return assumptions?
Yes. Returns, fees, mortgage rate, extra payments — every assumption comes pre-filled but is fully editable, per asset. Nothing is hidden; see Methodology for the full models.
Which stocks and regions can I use, and how far back does the data go?
Stocks are simulated per ticker from Yahoo Finance history, as far back as the ticker has traded. Real estate uses Zillow data by region — home values (ZHVI) from 2000 and rents (ZORI) from 2015, down to ZIP and neighborhood level — with property-tax rates from the U.S. Census ACS (2005 onward).
Where does the data come from?
From public sources: Yahoo Finance (stocks), Zillow ZHVI and ZORI (real estate), FRED (the Fed funds reference rate), and the U.S. Census ACS (property tax). Providers, coverage windows, and update cadence are listed on the Data Sources page.
How current is the data?
Market and index data is refreshed by our pipeline on a regular schedule, and each simulation rolls back from the most recent settled month. Where a month has no published value — such as the Fed rate — the most recent prior value is carried forward.
How many assets can I compare?
From one to several. Run a single asset on its own or line several up side by side — each gets its own editable card and a line on the shared chart.
Are fees included?
Yes. Fund fees are deducted against the month-end balance, so the headline value is always net of cost. Taxes — income, dividend, and capital-gains — are not modeled; every result is pre-tax. See Methodology → Known limitations.
Are the results adjusted for inflation?
No. Every value is nominal — shown in the dollars of its own time, with no CPI deflation or real-dollar mode. See Methodology → Known limitations.
Does the Fed funds rate line change my results?
No. It's drawn behind the chart for context only, to show the rate environment your investment lived through. Every asset value would be identical with the line removed.
Why do some numbers look surprising (a high CAGR, or a low starting value)?
A few results have honest quirks: CAGR reads high when most of your money arrives through later contributions, and real-estate portfolio value starts below your down payment because sale costs are front-loaded. Each model's page in Methodology explains exactly how its own numbers behave.
What happens to the numbers I enter?
Your inputs are used only to compute the comparison — they aren't tied to an account. Saving and sharing scenarios is coming and will require signing in.