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What your portfolio does in a crash, before one happens.

Everyone knows how they would behave in a crash until they are in one. Pick a window the market has already lived through, and watch the book you hold today fall through it: the worst session, the bottom, and how long it stayed under the level it started from.

> chamberFeb 19, 2020 → Sep 4, 2020daily closes

COVID crash

The world shut down and the market repriced everything in five weeks — the fastest fall of its size on record, and the fastest recovery.

Your book

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Feb 19, 2020 — the last record high before the fall

-30%-20%-10%
peak
FebMarAprMayJunJulAugSep
s&p 500waiting for your holdings

Worst session

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Bottom

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Under water

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vs s&p 500

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Looking for your holdings…

> your book

reading your holdings

The chamber uses what you hold now and what those things did back then. It never asks when you bought — so it works the first time, with nothing imported.

Track this book in the terminal

Closes from Yahoo Finance for your holdings, and for the S&P 500 the window is measured against. Your book is carried through at today’s weights, so the chamber measures the portfolio you hold now, not the one you held then. Holdings that had not started trading are left out of the line and named above.

01how to read it
The bottom
deepest point vs the day it started

The number that decides whether you sell. Not the loss you took — the loss you were looking at.

The worst session
largest single move down

One day inside the fall. It is the day people remember, and usually the one they acted on.

Under water
from the peak to the day back above it

How long the decision had to hold. A fall you sit through costs nothing; the waiting is the price.

Each chamber runs from a peak to the day the index got back above it, so every window on this page contains its own recovery.

02what it does not do

This is a replay, not a forecast. It carries the weights you hold today through a window that already happened, which is a deliberate simplification: it assumes you held exactly this through the whole fall, bought nothing and sold nothing. Real portfolios are not held that still — people add, trim and panic. What the chamber gives you is the shape of the risk that is already in the book, measured against a crash the market has actually delivered.

Track the book, not just the crashor check how concentrated it is first →
03questions
Do I need an account to run the crash test?

No. Paste your holdings, or run the sample book, and the chamber replays immediately. The only thing sent to a server is the list of symbols, to fetch their closes for that window.

Does this predict the next crash?

No, and nothing can. The crash test replays windows that already happened, using the closes those holdings actually printed. It answers "what would this book have done in that", not "what happens next".

Why does it not ask when I bought?

Because it measures the portfolio you hold now. The chamber takes today's weights and carries them through a dated window, so a buy date would not change the answer. It also means the test works the first time, before any import.

Why is 2008 not one of the chambers?

The S&P 500 took five and a half years to get back above its 2007 high, and a large share of what people hold today was not listed yet. A window that long would measure the survivors rather than the crash. Every chamber here contains its own recovery, so the clock always has a day to count to.

What happens to a holding that did not exist back then?

It is left out of the line and named on screen, and the chamber says what share of the book the line actually speaks for. Nothing is quietly filled in with a proxy.

Where do the numbers come from?

Daily closes from Yahoo Finance for your holdings and for the S&P 500, gold and the STOXX 600, plus Brent from FRED. The comparator closes are baked into the page, so the same window always reads the same way.

Portfolio Crash Test — Your Holdings Through 2020, 2022 and 2024 | Portfolio Terminal