What Is Systemic Risk?

Michael Whitman · Trading since 2017, full-time since 2020 · YouTube creator, 137K subscribers · Published 2026-09-14 · Updated 2026-10-19

Most risks can be spread out until they stop mattering. This one cannot, and understanding why is the difference between a portfolio that is diversified and one that merely looks it.

How it works

A systemic event is one that propagates. One institution fails, its counterparties take losses, they fail or retrench, and the failure travels through the connections rather than stopping at the first holder.

Diversification is the standard defense against risk and it does not apply here. Spreading money across many holdings works because those holdings move somewhat independently. Systemic events remove the independence.

Correlations converge toward one. In a genuine crisis, assets that normally have little to do with each other fall together, because the reason they are falling is common to all of them — everyone needs cash at the same moment.

So the protection evaporates exactly when it is called on. That is not diversification failing to work; it is diversification working as specified, against a risk it was never designed for.

Systematic and unsystematic

Unsystematic risk is specific to one company. A factory fire, a failed product, a fraud. Hold thirty companies and any one of those becomes a small dent.

Systematic risk belongs to the market itself. Rates, recessions, liquidity. Holding more companies does not reduce it, because every one of them is exposed to the same thing.

And that distinction has a consequence for returns. The market pays you for bearing risk that cannot be diversified away, and does not pay you for bearing risk you could have removed for free — which is the argument for diversifying and the reason concentration is not rewarded.

A worked example

Take twenty positions of $5,000 each, $100,000 in all. If one company collapses by 60%, the portfolio loses $3,000, or 3% — a dent, which is diversification doing its job.

Now imagine a 40% decline across every holding at once. The portfolio does not experience twenty independent falls averaging out — it loses $40,000 in one simultaneous move, and the diversification contributed nothing.

That is what a systemic event does to the arithmetic. The expected benefit of spreading risk assumes the events are separate draws. When they are the same draw, twenty positions behave like one.

And the correlations measured in calm conditions are the ones people plan with. They are accurate for the period they were measured over and misleading about the period that matters.

What actually protects you

Position size. If a simultaneous decline across everything you hold is survivable, you survive it. That is the only defense that does not depend on holdings behaving differently from one another.

Holding assets with genuinely different mechanics, not merely different labels. Two equity funds in different countries are two equity positions.

And having cash. Not as a return-seeking position, but because the defining feature of a systemic event is that everyone needs cash at once, and whoever already has it is not forced to sell into it.

The original data

The S&P 500 carries the systemic record in a few lines. From its close of 1,565.15 on 9 Oct 2007 the index fell 56.8% to 676.53 by 9 Mar 2009 — a whole market’s worth of holdings falling together — and its longest wait below a prior record ran 1,897 trading days, from 11 Jan 1973 to 17 Jul 1980.

The 93% figure is the honest backdrop. Being under an earlier peak was the index’s normal state, true of 93% of its trading days since 1950, so a portfolio built on the assumption that declines are occasional and offsetting was mispriced from the start — before any systemic event was involved.

Why the connections are the mechanism

Systemic risk is a property of the network, not of any institution in it. A large bank failing in isolation is a large failure; the same bank failing while owing money to twenty others is a different event entirely, and the difference is the connections rather than the size.

That is why the phrase “too big to fail” is slightly wrong. The real criterion is too connected to fail — an institution sitting at the center of many obligations can be moderate in size and still bring down everything attached to it.

Leverage multiplies the propagation. A borrowed position forced to liquidate sells into a falling market, which pushes prices further down, which forces the next borrower to liquidate. That chain is mechanical rather than informational, and it runs at the speed of margin calls.

And it is why liquidity vanishes in exactly these conditions. The intermediaries who normally stand between buyers and sellers are themselves exposed, so they withdraw — which removes the shock absorber at the moment the shock arrives.

How this connects

Market risk is the portfolio name for the systematic kind. Beta measures how much of it a single holding carries, and a risk premium is what investors expect in return for bearing it.

Settlement risk and counterparty credit risk are the channels it travels through. A payment that never arrives, or a derivatives counterparty that cannot pay, is how one failure becomes several.

Liquidity risk is the accelerant. What the page describes as liquidity vanishing is liquidity risk appearing across the whole market at once, and a margin call is the instruction that turns it into forced selling.

Bank deposit risk is the household version. A run on one bank can spread to others through fear alone, which is the problem deposit insurance was built to stop.

The cash that protects has to be safe cash. A treasury bill or a money market fund holding government debt is what that defense usually means in practice, and a separate emergency fund keeps household needs from forcing a sale.

And tail risk is how it shows up in the worst outcomes a portfolio records, which is the exposure tail risk parity tries to size against directly.

When it fails

The characteristic failure is measuring correlation in calm conditions and sizing against it. The numbers are computed over the available history, most of which is ordinary, so they describe ordinary behavior. A portfolio sized to those correlations is implicitly assuming the relationship holds in the one scenario it was assembled to survive — and in that scenario the correlations are the first thing to change. The diversification is real right up to the moment it is needed.

A second failure is treating central clearing as elimination. It concentrates counterparty exposure in one institution, which makes that institution systemically important rather than making the risk go away.

A third is holding many funds that hold the same things, which is diversification on the statement and concentration in the portfolio.

A fourth is using leverage against a diversified book, since simultaneous declines and a margin requirement combine badly.

The question: Everything fell together. What was the hedge for?

And a fifth is assuming regulation removed it. Rules change where the risk sits; they do not delete the connections that make propagation possible.

Related

Counterparty risk covers the bilateral version that propagation is built from. Risk management covers position sizing, the defense that survives correlation. And diversification covers the protection that stops working here.

This page is educational, not financial advice. Test every idea on your own charts before risking money.