Marginal vs Cumulative RBA Hike Probability: Why One Number Isn't Enough
Our explainer on the ASX RBA Rate Tracker covers how a single meeting's probability is calculated. This one covers a sharper question: once you have that number for every upcoming meeting, what's the right way to read the sequence?
Most dashboards — including the standard ASX-style tracker — report one number per meeting: the chance that specific meeting delivers a move. That's a marginal probability. On its own, it can look unremarkable even while the underlying trend is building toward something far more decisive.
Two different questions, two different numbers
Marginal probability answers: "what's the chance this specific meeting delivers a move, given everything priced in up to the meeting before it?" Cumulative probability answers a different question: "what's the chance the rate is higher than today by this meeting?" The second number can only ever rise (or hold) meeting over meeting — it's a ratchet, not a series of independent coin flips, because once a hike happens the rate stays elevated unless there's an explicit cut.
Here's the live curve for the next four RBA meetings, read both ways:
| Meeting | Marginal hike prob | Cumulative hike prob (vs today) | Consensus |
|---|---|---|---|
| 03 Nov 2026 | Hold | ||
| 08 Dec 2026 | Hold | ||
| 02 Feb 2027 | Hold | ||
| 17 Mar 2027 | Hold |
Every one of those meetings is individually labelled "Hold," and no single meeting's marginal probability rises above 27%. Read in isolation, each looks like a low-conviction call. But the cumulative column tells the real story: by December, the market already prices a better-than-even (46%... then 67.6% by February) chance that a hike will have landed by that point versus today's 4.60%. By March 2027, that figure is above 90%.
How to get the cumulative number from the marginal one
If you only have marginal, meeting-by-meeting probabilities (as ASX and most trackers publish), you can't just read the cumulative story off a single line — you have to track it explicitly. The simplest version, assuming at most one 25 bp move is in play at a time: take the futures-implied rate for that meeting, subtract today's cash rate, and divide by 25 bps. That's the cumulative probability of having moved by then, vs today — not vs the previous meeting.
The marginal number for any meeting after the first is then just the difference between its cumulative figure and the one before it: marginal(N) = cumulative(N) − cumulative(N−1). Doing the subtraction the other way — inferring cumulative conviction from a list of marginal numbers without re-deriving it — is the mistake. The two series look similar enough at a glance that it's easy to read a modest marginal number as the whole story.
Why this matters more right now
This isn't an abstract point. The cash rate has already moved from 4.35% to 4.60% since mid-2026, and futures pricing for the next several meetings keeps climbing rather than flattening out — consistent with a market that expects the tightening to continue, not a one-off adjustment. A reader who only ever sees "Hold, 73%" for the next meeting could easily miss that the cumulative picture has already crossed the halfway point within two meetings.
None of this is a forecast — it's a direct read of what people are actually putting money behind in the ASX 30-day interbank cash rate futures market. But reading it correctly means asking which question you're actually answering: "will this meeting move?" or "will the rate have moved by this point?"