Black Swan

How far would your portfolio have fallen?

Build your portfolio, then replay it through the crashes that actually happened. This tool cannot tell you what the next crash holds — nobody can. It shows you how a mix like yours fell in 2008, in the COVID crash, in the dot-com bust, how deep the hole went and how long the market took to climb back out. The question it leaves you with is the only one that matters in a crash: could you have held?

Your portfolio

Portfolio value Total dollars invested today. It scales the dollar figures on your screen and nothing more — it never travels in a shared link, because the percentage a portfolio falls is a fact about a strategy, while a dollar loss is a fact about your net worth.

Your asset mix

Enter each sleeve as a percentage. They do not have to add up to exactly 100 — the tool normalises whatever you enter and shows you the running total. Start from a preset and change it, or type your own.

Start from:

US stocks S&P 500, total return. The anchor of most portfolios and the benchmark the recovery clock is measured against. International stocks Developed markets (MSCI EAFE), with emerging markets folded in. In 2008 it fell as hard as US stocks - crossing an ocean is not diversification when correlations go to one. US bonds (aggregate) The broad US investment-grade bond market. Cushioned the dot-com bust and the 2008 crisis - and fell 13% in 2022, its worst year since 1976, when the 60/40 broke. Long Treasuries 20-year-plus US government bonds. A powerful hedge in a flight to safety, and the sleeve that fell hardest of all in 2022 when rates rose. Gold Roughly doubled through 1973-74, and crashed 45% through 1980-82. It is not a switch that turns on in every crisis. Bitcoin No investable market before 2020, so it is excluded from every earlier crash. Where it did trade, it fell WITH stocks and harder - down 50% in the COVID crash. REITs Listed real estate. Rose through the dot-com bust and fell 68% in 2008 - the deepest drawdown of any sleeve in that crisis. Cash / T-bills Short Treasury bills. Nominally steady in every crash shown, but inflation quietly eroded it - deeply so in the 1970s and in 2022.

Were you still buying? I kept contributing every month through the crash

Pro

Build a custom crash

Set your own peak-to-trough drawdown for each sleeve and see what a scenario you define would do to this mix, alongside the real crashes.

Include my custom crash in the results Name this scenario

US stocks drawdown International stocks drawdown US bonds (aggregate) drawdown Long Treasuries drawdown Gold drawdown Bitcoin drawdown REITs drawdown Cash / T-bills drawdown

The free version replays three headline crashes — 2008, the COVID crash and the dot-com bust — in full, with the dip-buying readout and a shareable link. Pro replays all nine crashes back to 1929, compares portfolios side by side, adds a custom-crash builder, and unlocks image and CSV export.
The shareable link is free, for everyone, always. Pro is a separate one-time purchase — if you already subscribe to DCA Simulator Pro, this is not included in it.

Educational content only — not financial advice. Every figure here is a rounded, peak-to-trough index proxy from an event that actually happened, in US dollars, with no fees, tax or slippage. The portfolio drawdown assumes the sleeves bottomed together, which is close for an equity-heavy book and errs toward overstating the loss; recovery months are how long the US market took, not your specific mix. This is history replayed, not a guess about what comes next.