A concept that cannot be directly observed sits at the centre of the RBA's September reasoning: if the neutral interest rate has risen, a cash rate that once looked tight may not be doing as much work as assumed.

Ask a central banker whether interest rates are "high" and the honest answer is usually another question: high compared with what? The benchmark most often used is the neutral rate. At her media conference after the September decision, Governor Michele Bullock defined it as "the interest rate at which we think monetary policy is neither restrictive nor expansionary".

That definition may sound abstract, but it played a concrete role in the Monetary Policy Board's decision on 29 September 2026 to lift the cash rate target by 25 basis points to 4.60%.

What "neutral" means in practice

The idea is straightforward. When the cash rate is above neutral, policy is restrictive: borrowing is relatively expensive, which tends to slow spending and ease price pressures. When it is below neutral, policy is expansionary, encouraging borrowing and spending. At neutral, policy is neither pushing the economy forward nor holding it back.

The difficulty is that nobody can observe the neutral rate directly. It has to be estimated from economic models and the behaviour of the economy, and it can shift over time as conditions change. Note the Governor's phrasing: the rate at which "we think" policy is neutral. That qualifier signals a judgement rather than a measurement.

A few features of the concept are worth keeping in mind:

  • It is an estimate, not a published target. The RBA does not set the neutral rate; it tries to infer it.
  • It can move. Changes in productivity, global interest rates, investment demand and other forces can shift where neutral sits.
  • Its level determines how tight policy really is. The same cash rate can be strongly restrictive if neutral is low, or only mildly restrictive if neutral is high.

How neutral shaped the September decision

The minutes of the 28–29 September meeting set out the arguments for raising rates. One of them turned directly on this idea. Members noted that the previous cash rate of 4.35% may be "less restrictive" than it was two years earlier if the neutral rate has risen.

That is a significant observation. It suggests that even without a change in the cash rate, the degree of restraint on the economy could have quietly diminished. If so, holding at 4.35% would have meant policy doing less to slow inflation than the headline number implied. Members also judged that a timely response would best balance the Board's objectives, and that the existing setting might not restore balance in a reasonable timeframe.

The minutes also record a broader judgement: "Australian financial conditions remained somewhat restrictive", although the extent of that restriction was described as uncertain. Read together, the two passages describe a Board confident that policy is restrictive to some degree, but unsure by how much.

The stance of policy has also featured in recent RBA appearances. On 13 August 2026, Assistant Governor (Financial Markets) Christopher Kent gave a speech titled "The Restrictive Stance of Monetary Policy". The RBA speeches list records the title, speaker and date.

Why the question matters more now

Several features of the current environment make the neutral rate unusually relevant.

Inflation is above target. Headline CPI rose 4.0% over the year to August 2026 on the monthly measure. The trimmed mean, the RBA's preferred gauge of underlying inflation, was 3.6% over the year to the June quarter, when headline CPI was 3.9%. The target range is 2–3%. To bring inflation down, the RBA needs policy to be restrictive enough, which depends on where neutral sits.

Global yields have risen. The minutes note that global bond yields rose notably, mainly reflecting higher real yields, while long-term inflation expectations were broadly stable. Several central banks abroad have already raised rates. In general terms, real yields in global markets are among the factors economists consider when estimating neutral rates.

Demand pressures are building from new sources. "The AI boom is also adding to demand in the Australian economy at a time when we already have capacity pressures," Bullock said.

Productivity remains weak. Bullock was blunt on this point: "The bottom line is that productivity is doing nothing." She was also clear about the limits of her own tools: "monetary policy can't do anything about productivity."

Policy works with a lag. Bullock said rate changes take about 12 to 18 months to have their full effect. If policy is less restrictive than assumed, that could take time to become apparent in the data.

Uncertainty cuts both ways

The neutral rate argument is not a one-way case for higher rates. The minutes also record the case for holding in September: downside risks to activity and employment, a possibly larger-than-expected effect from falling housing prices, uncertainty in the Middle East and the lagged effects of earlier tightening. Housing prices have fallen in most capital cities, and scheduled mortgage payments have risen to around 10% of household disposable income, around their 2024 peak.

The Board's forward language reflects that uncertainty. It said it would be "attentive to the data and the evolving assessment of the outlook and risks to guide its decisions." Asked whether the latest increase would prove sufficient, Bullock said: "Now, will it be enough? I don't know."

For borrowers, the neutral rate debate can feel remote. But it shapes how the RBA interprets the economy's response to each rate change. Those trying to understand how such debates might affect their own finances may wish to seek licensed professional advice.

The bottom line

The neutral rate is the yardstick against which the RBA judges whether its policy is tight or loose, and it cannot be measured precisely. In September, the possibility that neutral has risen was one reason the Board judged 4.35% might no longer be restrictive enough. Bullock's careful definition, the rate at which "we think" policy is neutral, is a reminder that the answer is an estimate. That uncertainty will continue to shape the Board's reading of the data, starting with its next update on 3 November.