The oil contract that expired below zero
In April 2020 an expiring American crude contract settled beneath zero, and a lot of software met a case nobody had written down.
The morning a price went through a floor nobody had drawn
The mechanics were not mysterious. Demand for physical crude fell away that spring while barrels kept arriving, and the American benchmark contract obliges whoever holds it at expiry to receive oil in Oklahoma. Storage there was close to full, so holders with no tank paid others to take the obligation. Paying to be rid of something is a negative price.
The oil is the least interesting part. What makes the episode worth studying is that many products sold to people who had never seen a storage tank referenced that contract, and for a few hours did things their holders had not budgeted for. Read it as an investigator reads wreckage: find which assumptions were carrying weight unnoticed.
The famous number does no work here
The figure the contract settled at is the part everybody remembers, and it falls outside the dataset this piece may draw on, so it appears nowhere below. Nor do the per-firm write-offs or the client counts, which circulated afterwards in versions that disagreed with one another. Very little is lost by leaving them out, because magnitude was never where the finding lived. A price a penny below zero raises everything a price far below zero raises: whether the arithmetic downstream tolerates the sign, whether a risk model has a state for it, and who carries a liability with no floor. The size supplies the drama and the sign supplies the lesson.
Three different things people mean by impossible
The word does at least three jobs. There is the sense guaranteed by structure: an ordinary share cannot be worth less than nothing, because the owner walks away and limited liability handles the rest. There is the sense imposed by rule, where a system refuses an instruction because a regulator said so. And there is the sense meaning only that nothing resembling it appears in the record anybody consulted.
The third routinely gets handled as though it were the first, and that substitution is the mechanism. A price history whose lowest observed value sits above zero describes a sample. Read as a description of the instrument, it licenses a field to be typed, an axis drawn, a rule written.
Nobody decides something is impossible. People never meet the case, which has the same effect.
A minus sign is ordinary arithmetic and awkward plumbing
Mathematics raises no objection to a negative price. The objection lives in the machinery that carries a price around, which is full of quiet places where positivity gets assumed: fields typed to hold values above zero, chart scales beginning there, calculations taking the sign for granted, validation refusing an order priced beneath anything anybody expected.
The transferable lesson concerns where beliefs get stored. A belief about how the world behaves is rarely filed in a document with the word assumption on it. It sits in a data type, a default, a chart scale, a limit expressed as a share of a quantity presumed positive. The excluded case arriving is usually the first moment anybody discovers the belief was in there.
Where the belief was being kept What it amounted to How it behaved that week Was it written down anywhere first? A field typed to hold a price Prices are positive numbers Refused the value, or stored something else Only in whoever wrote the schema A chart axis starting at zero There is nothing below the bottom The line left the picture No, but anyone could see it A margin figure taken as a share of the price A share of a price is smaller than the price The arithmetic kept working and changed meaning In the client agreement, at best A validation rule rejecting odd prices Nobody deals below zero Refused instructions people wanted to give No A contract obliging delivery at one town Somebody will always want the barrels It held.
| The clause did what it said | Yes, in the contract specification | ||
| A rule capping a retail account at zero | The client’s loss stops at the balance | It held, and sent the tail somewhere else | Yes, in the handbook |
Six places a belief about prices can sit, what each one amounted to, and whether it had been written down before that week. The first four rows are constructed types rather than any named firm’s code.
Where the loss stops for a UK retail account
Almost nobody in Britain expressed a view on oil that spring by joining the queue for barrels. They did it through a contract for difference or a spread bet, and that distinction governs the answer. A retail client of an FCA-authorised firm offering those products has negative balance protection on the account, so the loss halts at the money sitting in it.
The word protection makes it sound as though the exposure went away. It moved. A loss below zero still occurred somewhere along the chain, and the rule decides who carries it, which here is the firm on the other side and whatever hedging it had arranged. A measure written for consumers doubles as a capital question for the firm.
Once the tail sits with the firm, the client’s question changes shape. The protection is an obligation of the company named on the agreement, met from that company’s own resources, so what it is worth on the worst morning depends on that company still functioning that morning. The rule is sound. Every promise nonetheless inherits the finances of whoever made it.
The uncomfortable feature is correlation. An event violent enough to test one client’s protection tests every client’s at the same instant, the opposite of the diversified picture the phrase per account invites. Underneath sits the compensation scheme, capped for each client at each firm and concerned with money the firm owed you rather than the position you ran.
The worst day is a poor teacher
Here is where the story spoils. Building a way of holding oil around one April is an error with a bill attached to every other month. The episode is memorable precisely because it is unrepresentative, and the overwhelming majority of retail oil positions have closed in conditions where none of this machinery was consulted. Financing on a long hold and a size chosen against a round number do more aggregate damage.
The method problem, stated plainly. Funded-account testing samples the dense middle of the distribution, because a tester can buy a position and cannot buy a dislocation to hold it through, so such a programme covers the ordinary month and is absent from the tail by design. A survey of the platforms that quote oil to British retail clients, published by The Investors Centre, which opens and funds live accounts with its own money to test UK trading platforms rather than compiling rankings from providers’ published fee schedules, can price a spread and time a withdrawal, and will be elsewhere entirely on the morning this article is about.
Aviation and medicine reached the same conclusion about investigations, which is that the value lies somewhere other than in the failure itself. The exercise produces a register of what everybody had been leaning on without saying so. April 2020 yielded a decent one: an instrument with no floor because it carried an obligation to receive a physical thing, and a chain downstream that had encoded a sample as a property.
So the output worth keeping is not a scenario to rehearse, it is a list of assumptions to go and locate. Three are readable this afternoon by anyone holding oil through a British account: what the product actually references, what your position does when that reference expires, and which legal entity owes you the protection when the balance goes.
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