About Our Data and Methodology | Clarity Capital Tools

A set of free tools for looking at how investments have actually behaved, using real historical market data rather than projections. This page covers where that data comes from and what each simulation assumes.

Where the data comes from

Robert Shiller — S&P 500 monthly series

monthly, from January 1871

Monthly index price and dividend data, published at shillerdata.com. This is the basis for the S&P 500 history, extremes, downturn and Monte Carlo pages — currently 154 complete calendar years, 1872 through 2025.
Aswath Damodaran, NYU Stern — annual asset class returns

annual, 1928–2025

Historical returns on stocks, bonds and bills. Used for the rolling-returns page, which shows forward 1, 3, 5, 7 and 10-year returns from each starting year.
Yahoo Finance — ETF prices and dividends

monthly high, low and close; dividend distributions

Powers the portfolio simulator, the sector pages and the ETF directory, which currently covers 81 non-leveraged ETFs across 8 categories.
FRED — federal funds rate

monthly

Used as the interest rate on uninvested cash, and as the money market benchmark the portfolio simulator compares against.

What the simulations assume

The assumptions below are deliberately conservative. Where a choice could flatter the result, the less favourable option is taken.

Purchases happen at each month's high price, not an average or a low — the worst entry price available that month.
Whole shares only. Cash that isn't enough for a full share stays in that holding's own bucket until it is.
Dividends are treated as cash received and are not reinvested. Reinvesting would produce higher figures; this shows the more modest path.
That cash earns the historical federal funds rate, compounded monthly, rather than sitting idle.
Simulations end in December of the last complete calendar year, so no result depends on a partial year.
If a holding wasn't tradeable in a given month, its share of that month's contribution is redistributed across the others and resumes when it becomes available.

The portfolio simulator's mechanics are covered in more detail in How the Simulator Works.

What these tools are, and are not

These are educational tools for exploring historical data. They describe what happened in the past over the periods you select.

They are not investment advice, and nothing here is a recommendation to buy or sell any security. No result produced here is a forecast.

Historical returns do not predict future returns. The Monte Carlo page in particular resamples real historical sequences to show a range of outcomes — that range reflects how markets have behaved before, not the full set of things that could happen next.

Figures are drawn from third-party data sources and may contain errors or revisions. Verify anything you intend to act on against the fund issuer's own published data.

About These Tools

Where the data comes from

What the simulations assume

What these tools are, and are not