How it unfolds, step by step
The setup
Two figures come from different selections of contracts. The first comes from an option chain. An option chain is the table listing every strike and expiry available on one underlying. It shows three call strikes — 100, 105 and 110 — carrying 2,000, 10,000 and 4,000 contracts of open interest. In a separate selection, the puts total 15,000 against 10,000 on the calls. So that selection has a put–call ratio of 1.5. Its call total is separate from the three strikes above.
What happens next
Both are then read as forecasts. The 105 strike becomes a level the underlying cannot pass, because that is where the sellers are. The 1.5 becomes a majority expecting a fall, or something close to a probability. In each case, two steps have been taken where the data supports one. Something was counted. Then a claim was made about what the holders of those contracts will do.
What it means — and does not
What the count supports is narrow, and worth stating in full. The largest call open interest in the chosen set is at strike 105, at the moment it was read, across the strikes and expiries that were chosen. Those positions can be closed. They can be moved into a later expiry. They can be held against exposure that sits somewhere else entirely. They can be the one visible part of a larger position, whose other parts sit in a column nobody is looking at. The ratio is maths on two chosen totals. 15,000 divided by 10,000 is 1.5, and that is the whole of what it is. It is not a probability. It is not a share of participants who hold a view. And it cannot be compared with a ratio built from volume instead of open interest, or across every expiry instead of the nearest one. Neither figure becomes evidence about direction until somebody writes down a claim that could have failed, and then did not.
What this does not establish
A reading like this is proved wrong by the design of the test, not by the chain. A statement worth checking declares five things. The input window. The set of contracts it covers. The moment the observation is taken. The horizon the outcome is measured over. And what counts as the outcome. To refute it, run that same rule on data it has never seen. If it does no better than the simplest baseline it is compared against, it is refuted. Most claims of this kind never get that far. They are stated after the move they explain. They are about the strikes that turned out to matter. And the window was chosen once the answer was known. A claim built that way cannot be refuted by anything. And a claim that nothing could refute is not evidence about the future. One more failure is quieter, and it is the honest one to own up to. Many likely-looking conditions are searched. The best-looking one is reported. The searching is not.
Things to check
6Is the statement a description of a count, or a claim about how people will behave?
Which strikes, which expiries and which moment does the figure actually cover?
Is the ratio built from open interest or from volume, and over which expiries?
Was the rule written down before the outcome was known, or fitted to it afterwards?
What would have had to happen for the reading to be wrong — and could it have happened?
Remember: participant intent is not published, so no count can identify who is behind it.
Common mistakes
5Describing the largest strike as a barrier. It is the largest number among whichever strikes were picked, and whoever drew the display picked them.
Reading a put–call ratio as a probability or as a headcount of opinion. It is one chosen total divided by another chosen total.
Comparing two ratios without saying what went into each. An open-interest ratio and a volume ratio, or a near-expiry ratio and an all-expiry ratio, are different measurements sharing one name.
Explaining a move afterwards with a count read beforehand and calling that a test. An explanation that could not have failed has not been tested.
Assuming a rise in open interest against a flat price names its own cause. New opposing views, protection bought against exposure held elsewhere, and one part of a larger position all produce the same two columns.
One call strike carries far more open interest than its neighbours. What has that established?
- That the underlying is unlikely to trade above that strike before expiry
- That sellers at that strike will defend it
- That more contracts are outstanding at that strike than at the others in the set that was looked at, at the moment it was read
Show the answer
C. That more contracts are outstanding at that strike than at the others in the set that was looked at, at the moment it was read
The count is a measurement. The other two answers are stories about how people will behave. Nothing in the number says what becomes of those positions. They can be held to expiry, closed the next morning, moved into a later expiry, or carried as protection against exposure that never appears in that column. The set of strikes being compared was also chosen by whoever drew the display. So "largest" is partly a fact about that choice. The first answer is the one worth watching for. It sounds careful, because it says "unlikely", but it slips in exactly the same unearned claim as the second.
Frequently asked
4Is open interest useless if it cannot forecast direction?
No. It describes how many are taking part and how many positions are outstanding. That is a real, checkable thing to know. The limit is on what follows from it, not on whether it is worth reading.
What is a put–call ratio?
It is the chosen put open interest divided by the chosen call open interest. Here 15,000 against 10,000 gives 1.5. The definition has to travel with the number. A ratio built from volume, or across all expiries rather than the nearest, is a different measurement wearing the same name.
Why is the largest open-interest strike not a wall?
Because a contract count is not a promise to defend a level. Those positions can be closed, moved into a later expiry, or held as protection against something else. The count says nothing about which of those it is.
What is max pain, and does it predict the expiry price?
Max pain is a sum worked out from one option chain. Pretend the index closes at one strike on expiry day. Add up what every open call and put would pay its buyers there. Do this for each strike. The strike with the smallest total is max pain. It is arithmetic on a count, not a forecast. Open interest keeps changing, so the answer can change too. And the price can end far from it.