Australia has three private house-price indices — Cotality, PropTrack, and Domain — built on three different methods and three cadences. They report on one housing market, and they routinely disagree. This brief places them side by side.
Two indices, one country, one month. The gap is not error — it is method. Cotality runs a daily hedonic regression; PropTrack runs a monthly repeat-sales-and-hedonic hybrid. Each number is correct under its own measurement.
It is one of the most-repeated sentences in Australian news: house prices rose, or fell, by a precise figure last month. The sentence sounds like a fact about the country. It is, more precisely, a fact about one company's measurement of the country.
There is no single Australian house price. There are several house-price indices — each one a private firm's estimate, built by its own method, published on its own cadence. When two of them measure the same month and print different numbers, neither is wrong. They are answering the same question with different instruments.
This brief takes the three indices an Australian reader actually encounters — Cotality, PropTrack, and Domain — and places their March 2026 numbers on one sheet. The point is not to crown a winner. It is to show that the figure in the headline is a measurement choice, and that a reader who does not know which index produced it, over which window, does not yet know what the number says.
For March 2026, the two indices that report monthly disagreed by more than two-to-one at the national level. Step down to a single city, and the gap holds. The chart below is built only from each publisher's own released figures.
| Index | Publisher | Method & cadence | March 2026, national |
|---|---|---|---|
| Home Value Index | Cotality (formerly CoreLogic) | Hedonic regression · daily | +0.7% month · +9.9% year · median A$933,137 |
| Home Price Index | REA Group / PropTrack | Hybrid repeat-sales + hedonic · monthly | +0.3% month · +9.4% year · median ~A$908,000 |
| House Price Report | Domain | Stratified (mix-adjusted) median · quarterly | Reported by capital city — Sydney house median A$1,791,643 |
| Residential Property Price Index | ABS — official | — | discontinued after December 2021 |
Two facts sit in that chart. First, the national monthly figure: Cotality's Home Value Index recorded +0.7% for March 2026, PropTrack's Home Price Index +0.3% — the same month, the same idea of a national monthly change, and a gap of roughly 2.3 times. The national median levels differ too: Cotality's A$933,137 against PropTrack's roughly A$908,000, about A$25,000 apart.
Second, the single-city figure. For Sydney houses across the March quarter 2026, both indices recorded a decline — but Domain put it at −0.04%, barely a move (a A$772 dip on a A$1.79 million median), while Cotality put it at −0.6%, a clear quarterly fall. Same city, same asset class, same three months: the two agree the market fell, and disagree — by roughly half a percentage point — on how far.
Every house-price index faces the same difficulty: the mix of homes that sells changes from period to period. A month heavy with mansion sales is not a month the market rose. Each index controls for that differently — and that is where the numbers part.
None of the three is the error. A hedonic regression, a repeat-sales hybrid, and a stratified median are all established, defensible ways to measure a housing market — each makes a different trade-off, revises on a different schedule, and reports on a different cadence. Run them over the same three months and they will, more often than not, produce three different numbers.
There is also a cadence trap underneath the method trap. Cotality publishes a daily index; PropTrack a monthly one; Domain a quarterly report. A “this month” Cotality move and a “this quarter” Domain move are not the same measurement period at all — so even before the methods diverge, the windows already have.
A reader comparing three private indices might reasonably ask: is there an official one? A government series, the neutral reference? There was. The Australian Bureau of Statistics Residential Property Price Indexes: Eight Capital Cities — catalogue 6416.0 — was exactly that.
It ceased publication after the December quarter 2021. The ABS release page now carries a single line: “This release has Ceased.” There is no current official ABS house-price index.
What ceased was the constant-quality index — the mix-adjusted measure. The ABS still publishes official residential price levels, quarterly, in its Total Value of Dwellings release: a national mean price of residential dwellings (Table 1, all series — A$1,074,700 for the December quarter 2025, up A$28,700 on the quarter) and a median price by capital city (Table 2). These are price levels, not a mix-adjusted index — they track what dwellings cost, but they do not control for the changing mix of what sells the way the hedonic and stratified indices above do. So the finding is narrower than “no official price data”: what Australia lost in 2021 was the official constant-quality price index, not an official price measure.
So the picture is precise: every house-price index an Australian encounters in the news — the daily, monthly and quarterly numbers that move the market — is privately published. The ABS still measures residential prices in levels; the official mix-adjusted index a reader might assume sits behind the headlines is the part that was retired in 2021.
AU-01 opens The Australian Property Decode — a RAOSCAFF series that takes the published research of the Australian property market, from the global advisory firms to the domestic data houses, and decomposes what each headline leaves unsaid.
It begins, deliberately, with the most basic number of all — the house price — and the finding that there is no single one. Every brief that follows rests on a number a publisher released; this one rests on the fact that three publishers released three.
General information only. The scenario below is a modelled illustration, built to make the data concrete — it is not advice, and it describes no real person, household, or transaction.
Picture a household in a modelled middle-ring Sydney suburb, weighing whether to put their house on the market this autumn. They do what most people do: they read. One article, citing one index, tells them Sydney values were barely changed this quarter — down only a fraction, no urgency. Another, citing a different index, tells them Sydney houses fell clearly through the quarter — a reason to move sooner. Both readings are, in fact, negative: both indices have Sydney houses down for the quarter.
Both articles are accurate. Both quote a real, released figure. The household is not reading conflicting opinions — it is reading two instruments, a stratified-median quarterly report and a hedonic daily index, measuring the same three months and landing about half a percentage point apart. Neither article tends to say which instrument it used, or that another instrument exists.
This composite is illustrative — a modelled household, not a survey of one. Its only purpose is to make the divergence concrete: the gap between the indices is not an abstraction on a chart. It is the difference between “wait” and “list now” for a reader who never saw the methodology footnote. The brief's response is not advice on what the household should do — it is simply that they should know which index they are reading.
If you read one thing: a house-price headline is a measurement choice. Before you trust the number, check which index produced it, by which method, over which window.
Australia's house-price number is not one number. It is three private index measurements — a daily hedonic index, a monthly hybrid index, a quarterly stratified median — while the official, mix-adjusted ABS index no longer exists (the ABS still publishes price levels, not an index). Mirror Brief AU-01 makes one claim: the house-price figure in a headline is a measurement choice — read which index produced it, by which method, over which window, before reading it as the price of Australia. Every figure here is verbatim from a publisher's own release. The brief alleges nothing against Cotality, PropTrack, Domain, or the ABS — each index is correct under its own method. It places the measurements side by side; the reader reads the divergence.
Mirror format — RAOSCAFF anchors on the publishers' own released figures (Cotality, PropTrack, Domain), places the three indices on one comparison sheet, and decomposes the methodology that makes them diverge. No primary data collection, no analyst estimate, no extrapolation. The brief reports what the publishers reported.
Every figure traces to a March 2026 or March-quarter 2026 publisher release, or to clearly-attributed reputable press coverage of that release, fetched live on 21 May 2026 across a two-round verification pass. Where a figure could not be verified to a primary source — PropTrack's March city-level changes — it is not cited. Full source list in the companion FACTS.md.
FACTS.md is the source-of-truth file; every figure in this report traces to it. Phase 0 verification caught and corrected one structural error: the brief was originally scoped around four indices including the ABS, but the ABS Residential Property Price Index ceased publication after December 2021 — so the brief was reframed to three private indices plus the discontinued-official-index finding.
PropTrack city-level March figures are not cited (not verifiable to a primary source at the time of writing). Domain's national house-price aggregate is not cited (Domain reports by capital city). The brief does not adjudicate which index is most accurate, and it makes no forecast of Australian house prices.
Predict-not-recommend. Defamation-disciplined: the brief critiques index methods, definitions, and cadences — never the integrity or competence of any publisher or person; each index is stated to be correct under its own method. The Australian Bureau of Statistics, Cotality, PropTrack, and Domain are cited as the authoritative publishers of their respective series. The brief adds only the cross-index comparison no single publisher prints.