How Queensland home price indexes work, and why they give different numbers

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Kooky

Builder of Shaka, the payment router that pays every agent their commission on closing date.

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In the space of two weeks, a Queenslander following the property pages could have read that Brisbane home values rose 0.9 per cent in May, that they rose 0.1 per cent in May, that the typical Brisbane home is worth $1,126,149, that the median Greater Brisbane house sold for $1.15 million, and that the average Queensland dwelling is worth $1,123,700. Every one of those figures came from a reputable source. None of them is wrong.

They differ because they do not measure the same thing. Some count only the homes that sold; others estimate a value for every home in the state. Some report the middle sale price; others report an average, or an index with no dollar sign at all. Some cover a month, some a quarter, some a year.

This guide explains the main methods in plain terms, then goes through the four measures Queensland readers meet most often: the Cotality Home Value Index, the PropTrack Home Price Index, the ABS Total Value of Dwellings and the REIQ's medians. It draws on what each organisation publishes about its own method.

Cotality Home Value Index, 1 June 2026; PropTrack figure as reported by Real Estate Business, 8 June 2026; turnover estimate from the Reserve Bank of Australia Bulletin, June 2006.

Five figures for one market

The clearest way to see the problem is to put the published numbers next to each other, with what each one counts.

Three choices separate these numbers: which homes are counted (those sold, or all of them), which summary is used (the middle value, or the average), and which area and period are covered. The rest of this guide takes those choices one at a time.

The simple median, and its weak point

The most familiar measure is the median sale price. The REIQ defines it in the notes to its market releases: sale prices are arranged from lowest to highest and the middle value is taken, so that half the recorded sales were below it and half above.

A median is easy to understand and hard to distort with one extraordinary sale. Its weakness is that it only describes the homes that happened to sell, and those change from one period to the next.

The Reserve Bank of Australia set out the problem in a Bulletin article on measuring housing prices in June 2006. Only a small fraction of the housing stock changes hands in any period: about 1.5 per cent a quarter in Australia, on its estimate. If this quarter's sales include more homes from expensive suburbs than last quarter's, the median rises even if no individual home is worth a dollar more. Statisticians call this compositional change, or simply the mix.

The effect is not small. In the same article, the Reserve Bank found that around 60 per cent of the quarterly variation in median price changes in Sydney and Melbourne came from shifts in the mix of sales between dearer and cheaper suburbs, not from price movements. It also found a seasonal pattern, with more expensive houses tending to sell in the December quarter.

Timing adds a second problem. The Reserve Bank noted a lag of typically one to three months between agreeing a price and settling the sale, so the record of a sale can arrive months after the deal. A median published promptly is built on the sales known so far.

Stratified medians: sort first, then measure

The first repair is called stratification, or mix adjustment. Sales are sorted into groups that are alike, a median or mean is taken within each group, and the results are combined using fixed weights. If one group happens to have a busy quarter, it does not drag the overall figure with it.

The groups can be regions, dwelling types, or both. A Reserve Bank research paper published in May 2006 proposed grouping suburbs by their long-term price level, so that cheaper and dearer suburbs are kept apart, and found that this substantially improved on the plain median while staying simple to compute.

Two measures Queensland readers see use this idea. Domain states in its quarterly House Price Report that its capital city figures are stratified medians, while other geographies use a middle sale price. And the ABS, as described below, stratifies by location and dwelling type to value the whole dwelling stock.

Stratification deals with shifts between areas and types. It does not deal with shifts inside a group: if the houses sold in a suburb this quarter are larger or better renovated than last quarter's, a stratified median still moves.

Hedonic indexes: pricing the features

The second repair goes further. A hedonic index starts from the idea, as Cotality puts it in its methodology notes, that the value of a composite good such as a house is the sum of its components. A statistical model looks at thousands of sales and estimates how much buyers are paying for each feature: an extra bedroom, a larger block, a given location.

Once those estimates exist, the price change of a like-for-like home can be separated from the change in what was sold. The Reserve Bank's 2006 article describes the approach as explaining each transaction price by attributes such as location, type and size, together with the period of sale.

The method has costs, which the Reserve Bank also listed: it needs complex statistics, detailed data on the features of homes, and choices by whoever builds the model. Two careful teams with different data and different models will not produce identical answers. That is the main reason Cotality and PropTrack, which both use hedonic methods, can report different figures for the same city in the same month.

Repeat-sales indexes: the same home, twice

A third family avoids the question of features altogether. A repeat-sales index looks only at homes that have sold more than once and measures the change in price between the two sales. Because it is the same home, location and land size are held constant automatically.

The Reserve Bank's article points to two limits. The method uses only those transactions for which an earlier sale is on record, which discards the rest. And its estimates need continual revision, because every new sale of a home changes the measured growth for the whole period since its previous sale. A home can also change between sales, through renovation or neglect, without the method knowing.

Neither of the two monthly indexes most quoted in Queensland describes itself as a repeat-sales index today: Cotality and PropTrack both publish hedonic measures. Repeat sales remain worth understanding because the idea, comparing a home with itself, is the intuition most owners already use.

The Reserve Bank's comparison is reassuring about all three advanced approaches. It found that mix-adjusted, hedonic and repeat-sales measures contained around 70 per cent less noise than the raw median, and moved closely together, with a correlation of about 0.9.

Cotality's Home Value Index

Cotality, formerly CoreLogic, publishes its Home Value Index on the first business day of each month. It is a hedonic index of a particular kind: Cotality calls its method hedonic imputation. The model does not stop at measuring price change among homes that sold. It uses recent sales, and the characteristics of the homes involved, to estimate a current value for dwellings that have not sold.

That is why Cotality can publish a "median value" for Brisbane that is not a median sale price. The $1,126,149 quoted for May 2026 is the middle of the estimated values of all dwellings in Greater Brisbane, houses and units together. It can sit above or below the median price of the homes that sold in the same month.

Cotality says the attributes in its model include the number of bedrooms and bathrooms, land area and geographic location, and that its sales data come from state property registries, which for this state means the Queensland Government's records. The index is produced for many geographies, from the national level down to suburbs, postcodes and council areas, and a daily version exists alongside the monthly one.

The feature that matters most to readers is the revision policy. Cotality states that its indices are revised each month for twelve months after first publication. The first figure for any month is an estimate made before all of that month's sales have been recorded.

PropTrack's Home Price Index

PropTrack is the property data business of REA Group, which operates realestate.com.au. Its Home Price Index is also released on the first business day of each month, according to PropTrack's published questions and answers.

Its methodology document, updated in July 2025, describes an adjacent period hedonic imputation method that measures changes in home values by adjusting for differences in the attributes of the properties sold. The regression uses 19 variables. Some are familiar, such as bedrooms, bathrooms, garages, land area and living area; others are drawn from building data, including roof type and material, building volume, swimming pools and solar panels.

The sales records come from the valuer-general's office in each state and territory. PropTrack supplements them with listings from realestate.com.au to cover the delay before official records arrive, which its document puts at typically twelve weeks. Transactions under $10,000 or above $50 million, statistical outliers, sales that are not at arm's length, and land, acreage and rural properties are filtered out.

PropTrack's index is in nominal dollars, with no adjustment for inflation. It is also revised more deeply than Cotality's: the methodology says the latest three years are recalculated every month, which PropTrack argues avoids large one-off revisions when late records are added.

The ABS Total Value of Dwellings

The Australian Bureau of Statistics no longer publishes a house price index of the old kind. Its Residential Property Price Index stopped in December 2021. What it publishes each quarter is the Total Value of Dwellings: an estimate of the number of residential dwellings in each state, their mean price and their total value.

The ABS methodology explains how. The count of dwellings starts from the latest Census and is updated with building completions. Prices come from sales data supplied by CoreLogic, now Cotality, which originate with state land titles and valuer-general offices. The ABS stratifies by location and dwelling type, calculates a mean price in each cell from the homes that sold, and applies it to the homes that did not.

Three things follow for anyone quoting the result. The headline is a mean, the average, and the ABS itself asks users to exercise caution when comparing it with medians. It covers every residential dwelling in the state, houses and units, city and country, including government-owned and rented homes. And it is quarterly and slow: the March quarter 2026 figures were released on 9 June.

It is also preliminary at first. The ABS says the latest quarter's estimate uses Cotality's hedonic index as a proxy for price change, and that the two previous quarters are revised with each release, the third most recent quarter being treated as final. Alongside the means, the ABS publishes unstratified median prices and the number of transfers for established houses and attached dwellings, by capital city and rest of state.

REIQ medians in the Queensland Market Monitor

The Real Estate Institute of Queensland reports median sale prices each quarter for the state, for Greater Brisbane and for council areas and suburbs, in its Queensland Market Monitor and the media releases that accompany it. Its notes say the insights are derived by the REIQ from Cotality data.

These are medians of recorded sales, with houses and units reported separately. Two versions appear side by side. The quarterly median covers sales in the three months; the annual median covers sales over twelve months. For the March quarter 2026, the REIQ reported a statewide quarterly house median of $990,000 and an annual house median of $917,500. In a rising market the quarterly figure is higher, because the annual figure still contains sales made at earlier, lower prices.

The REIQ is open about the limits of small samples. Its notes state that only suburbs and regions with at least 10 sales for the quarter at the time of reporting are considered statistically significant. Ten is a low bar, and a median built on a dozen sales can jump for reasons that have nothing to do with values.

What the REIQ medians offer in exchange is closeness to the transaction. They are the prices buyers actually paid, in named council areas, in a recent quarter, which is exactly what an agent appraising a home or a buyer comparing suburbs wants to see.

Why first estimates change

Revisions are a sign of method, not of error. PropTrack's published answers make the point that being revisionary is common to almost all economic indicators, including labour market and national accounts figures. The practical lesson is to treat a single month's movement, especially a small one, as provisional, and to give more weight to the direction over several months.

Matching the measure to the question

No single figure is best for every purpose. The useful habit is to ask what the number was built to answer.

Two rules of thumb follow from everything above. Compare like with like: a figure from one provider should be set against the same provider's earlier figure, never against another's. And read the label before the number: sold homes or all homes, median or mean, houses or all dwellings, a month or a year, a suburb or the whole of Greater Brisbane.

The indexes disagree because they answer different questions. Knowing which question each one answers is most of the skill in reading them.

None of these measures values an individual home. Each describes a market, at a scale from a suburb to a state, and each does it with a method its publisher explains in public. The differences between them are the price of measuring something as varied as housing, and they are much easier to live with once the methods are familiar.

Kooky, from Shaka

Kooky edits Queensland Estate and builds Shaka, the payment router he made for Queensland property professionals. One payment comes in, and every agent, agency and party in the deal receives their signed share on closing date.

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