Two reputable publishers ask how long it takes to save a home deposit. One answers 11 years; the other, 5. This brief decomposes the gap between the answers.
Cotality's Housing Affordability Report puts it at 11.0 years; Domain's First-Home Buyer Report at 5 years and 0 months. Same question, two assumption sets — and the gap between the answers is the gap between the assumptions, not an error by either publisher.
A figure circulates through Australian housing coverage: it takes so many years to save a home deposit. It is repeated the way measured facts are repeated. It is not a measured fact — and it is not one number.
Two reputable publishers ask what looks like the same question and answer it differently. Cotality, in its Housing Affordability Report of November 2025, puts the time to save a 20% deposit at 11.0 years nationally. Domain, in its First-Home Buyer Report 2026 of February 2026, puts it at 5 years and 0 months. The two answers are 6.0 years apart — the longer about 2.2 times the shorter — and no statistical agency publishes a single figure that would settle which is “the” number. The “gap” this brief decomposes is that distance between two publishers' answers — not a gap between what a buyer has saved and what a buyer needs.
This brief decomposes that figure. The point is not that one publisher is wrong — each computes its figure correctly, under assumptions it states plainly. It is that the question “how many years?” is under-specified: it has no single answer until three things are named — who is saving, at what rate, and toward which home.
The question has no answer until three things are named — who is saving, at what rate, toward which home. Cotality and Domain name all three, and name them differently.
| The assumption | Cotality — 11.0 years | Domain — 5 years 0 months |
|---|---|---|
| Who is saving | one median-income household | a dual-income couple, both earning |
| The savings rate | 15% of gross (pre-tax) income | 20% of post-tax income, per person |
| What they are buying | the median dwelling — value $860,529 | an entry-level home — the 25th-percentile price |
Three modelling choices — the saver, the savings rate, the target home (the savings-rate choice itself carrying two differences: the rate, and whether it is taken from gross or post-tax income) — and each one, on its own, shortens or lengthens the answer. Two earners saving in parallel reach a target faster than one. A 20% deposit on a cheaper, entry-level home is a smaller dollar sum than 20% of the median dwelling. Compounded, the three choices move the answer from 11.0 years to 5.0.
Neither publisher is wrong. Cotality answers one question — how long for a median-income household, saving 15% of gross income, to reach a deposit on a median dwelling? Domain answers another — how long for a dual-income couple, each saving 20% of post-tax income, to reach a deposit on an entry-level home? These are different questions that share a surface wording. The 6.0-year gap is the distance between them.
No one measures how long a deposit takes. The figure is arithmetic on three chosen inputs — and the Cotality figure reconciles exactly to its own.
The Cotality figure can be rebuilt from its published inputs. A 20% deposit on the median dwelling value of $860,529 is $172,106. Saving 15% of a median gross household income of $104,390 a year is $15,658.50 a year — an income figure Cotality draws from the ANU Centre for Social Policy Research. And $172,106 ÷ $15,658.50 is about 11.0 years. The figure reconciles: it is arithmetic on three chosen inputs — a deposit target, an income, a savings rate — not a measurement of how long anyone actually took.
| Change one input | Years to save | What moved |
|---|---|---|
| Savings rate 10% of gross income | ≈ 16.5 yrs | a lower rate saves less each year — the figure lengthens |
| Savings rate 15% — Cotality's figure | ≈ 11.0 yrs | the published figure — the point Cotality's inputs produce |
| Savings rate 30% of gross income | ≈ 5.5 yrs | a higher rate saves more each year — the figure shortens |
| Savings rate 45% of gross income | ≈ 3.7 yrs | the upper end of the share a household directs to housing — the figure shortens further |
Because the figure is a calculation, changing one input changes the answer — by years. The table above is RAOSCAFF arithmetic, holding Cotality's other inputs fixed: it is illustrative sensitivity, not a Cotality figure and not a forecast. The realistic range is wide: a household saving for a home often directs far more than 15% of income to housing — guidance commonly frames 35% to 45% of gross income as the housing-payment share, and at a 45% rate the same deposit reconciles to about 3.7 years. The figure is also linear in the deposit target — at the same $15,658.50 saved a year, a 10% deposit reconciles to about 5.5 years and a 5% deposit to about 2.7 — these deposit-target figures, like the table above, are RAOSCAFF arithmetic, illustrative. The published figure is one point on a wide range: the point that follows from the inputs the publisher chose. AU-11 rebuilds Cotality's figure because all three of its inputs are published numerically; Domain's full input set is not reproduced in its report, so AU-11 reports Domain's figure with the assumptions Domain states rather than re-deriving it — a scope choice, not a ranking of the two publishers.
Set the publisher gap aside. A handful of assumptions sit inside almost any “years to save a deposit” figure — and one sizeable cost sits outside it.
The 20% deposit is a convention, not a requirement. Both publishers compute the time to save a 20% deposit. Twenty per cent is not a legal minimum. Domain states plainly that it uses 20% as the deposit to avoid lenders mortgage insurance — a convention, chosen for a reason, not a rule. In practice many first-home buyers purchase with a smaller deposit, and because the figure is linear in the target, a smaller deposit shortens every figure here proportionately — a 10% deposit roughly halves the time, and a 5% deposit (sufficient for an owner-occupier purchase — with lenders mortgage insurance, or none under the government 5% scheme) cuts it to about a quarter. The low-deposit pathway itself — the 5% deposit and the scheme that removes its mortgage insurance — is decomposed separately in AU-12.
The deposit is not the whole of the cash a buyer needs. “Years to save a deposit” measures the deposit alone. The sum a buyer must actually assemble to transact is larger — it also carries the transaction costs the figure leaves out: stamp duty (a state tax on a sliding scale, with first-home-buyer concessions or exemptions in most states) and, on a deposit below 20%, lenders mortgage insurance. Together these can add up to roughly 7% of the price on top of the deposit — a sum a buyer saving only “the deposit” has not counted. This brief decomposes the published deposit figure and records that the deposit is one component of the entry cost, not the whole.
The price is held static while the saver saves. Both models compute the years by fixing the target price at today's level for the whole saving period. This is a transparent modelling choice — it makes the calculation tractable — and it is an assumption. In the published data the price has not been static: Cotality's own release records national dwelling values up about 6.3% over the year to September 2025. A figure computed against a fixed target and a figure computed against a moving target answer slightly different questions. This brief reports the static-price figures exactly as each publisher computes them, and records that the assumption is there.
The figure is a national median over a wide range. “11.0 years” is a single national number, and it is a midpoint. Cotality's own report, for houses, runs from about 6.8 years in Darwin to about 16.7 years in Sydney — the national house figure of 11.9 years sits between them. A reader in any one city is not described by the national figure; the national figure is an average of places that differ by roughly ten years.
AU-11 continues the second slate of The Australian Property Decode. The series has decomposed how Australia measures the price of a house, the rent, the borrower, the auction, the build-to-rent pipeline, the supply shortfall, the vacancy rate, the building approvals, the size of a new loan, and the aggregate value of all the housing. The eleventh brief decomposes the figure for how long it takes to save the deposit that comes before a purchase.
It sits beside two earlier briefs on a household-finance thread: AU-08 decomposed the size of a new home loan, AU-10 the aggregate value of the housing stock and the debt against it, and AU-11 the figure for the deposit that precedes a loan. The series asks one question of each published property number: which population, which moment, which measure does this number actually describe? Here the answer is unusual — the number has no single value at all. Eleven headline numbers; eleven decompositions; one habit — read what the number is before reading what it says.
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 modelled would-be first-home buyer reading the housing news. In one place they read that it takes 11 years to save a deposit; in another, 5 years. They assume one of the two must be wrong.
Neither is. The 11 describes one median-income household saving 15% of its gross income toward the median dwelling. The 5 describes a dual-income couple, both earning, each saving 20% of post-tax income toward an entry-level home. They are two true figures — and the reader has been comparing them as if they answered the same question, when they answer two different ones.
What would tell this modelled reader more is not which number to trust, but which number describes them: how many incomes are saving, at what rate, toward which home. Once those three are named, one figure or the other — or a third, computed from their own inputs — becomes the relevant one. The headline alone cannot say which.
The composite is illustrative — a modelled reader, not a surveyed one. Its only purpose is to make the decomposition concrete: “years to save a deposit” is a model output, and the assumptions decide the answer. The brief offers no view on this reader's finances or what they should do — only on what each figure measures, and does not.
If you read one thing: “years to save a deposit” is a model output, not a measurement — and its assumptions decide the answer.
Australia's “years to save a home deposit” figure is not a measured fact and not a single number. Two reputable publishers, asking what looks like one question, answer it 6.0 years apart: Cotality's Housing Affordability Report of November 2025 puts the time to save a 20% deposit at 11.0 years nationally; Domain's First-Home Buyer Report 2026 of February 2026 puts it at 5 years and 0 months. The longer answer is about 2.2 times the shorter — and no statistical agency publishes a figure that would settle which is “the” number, because each is a model output, not a measurement. The gap is the assumption set: the question cannot be answered until the saver, the savings rate, and the target home are specified, and the two publishers specify all three differently — one median-income household versus a dual-income couple; 15% of gross income versus 20% of post-tax income per person; the median dwelling versus an entry-level home. Each figure is correct under its own assumptions. The figure is also a calculation — Cotality's reconciles exactly to its inputs ($172,106 ÷ $15,658.50 ≈ 11.0 years) and moves by years when an input moves — and three assumptions sit inside both — a 20% deposit that is a convention rather than a requirement, a price held static while the saver saves, and a national median that masks a city range of roughly ten years — while one sizeable cost sits outside the figure: the transaction costs (stamp duty, and lenders mortgage insurance below a 20% deposit), up to roughly 7% of the price, that the deposit number does not count. Mirror Brief AU-11 makes one claim: read “years to save a deposit” as a model output whose answer is set by its assumptions — name the saver, the rate, and the home before comparing two figures. Every publisher figure here is taken directly from Cotality's and Domain's own reports; the deposit and annual saving, the gap, the ratio, and the sensitivities are RAOSCAFF arithmetic from those inputs, labelled as derived. The brief alleges nothing against either publisher — both compute their figures correctly and state their assumptions openly; the brief's point is about how a model output is read in public.
Mirror format — RAOSCAFF anchors on the publishers' own filed reports and decomposes the figures they print. AU-11 is a twin-publisher brief: Cotality's Housing Affordability Report — Australia (November 2025) supplies one answer, its assumptions, and its city detail; Domain's First-Home Buyer Report 2026 (February 2026) supplies the other answer and its assumptions. The “years to save a deposit” figure is decomposed as what it structurally is — a model output, assumption-dependent, with a 6.0-year gap between two reasonable publishers. No primary data collection, no analyst estimate, no extrapolation.
Every figure traces to a named publisher report with its release date: Cotality (November 2025, metrics to the September 2025 quarter) and Domain (released 26 February 2026). The Cotality figure was reconciled from its three published inputs — a 20% deposit on the $860,529 median dwelling value, divided by 15% of the $104,390 median gross household income — and the arithmetic holds (≈ 11.0 years; the small residual is rounding). Domain's figure is reported with the assumptions Domain states; Domain's full input set is not re-derived here. Full source list in the companion FACTS.md.
FACTS.md is the source-of-truth file; every figure in this report traces to it. The hero is a paired-bar panel — Cotality's 11.0 years and Domain's 5.0 years drawn as proportionate bars on one shared scale, each with the three assumptions that produce it stacked beneath, and the 6.0-year gap between the answers marked. Every publisher figure is taken directly from the reports; the derived figures — the 6.0-year gap, the 2.2× ratio, and the savings-rate and deposit-target sensitivities — are RAOSCAFF arithmetic from those inputs, and are labelled as derived and illustrative.
AU-11 decomposes two publishers' reports; it is not an exhaustive survey of every published deposit-timeframe figure. The figures are model outputs, not survey measurements of how long buyers actually took. AU-11 does not adjudicate between the two publishers, and reconciles only the Cotality figure, whose inputs are all public; it notes the 20%-deposit convention, the transaction costs (stamp duty, lenders mortgage insurance) the deposit figure excludes, and that a smaller deposit shortens the figure; the low-deposit pathway and deposit-assistance scheme are decomposed in AU-12, not re-derived here. It forecasts nothing and attributes the level of prices, incomes, or timeframes to no cause.
Predict-not-recommend. Defamation-disciplined: the brief critiques what the metric measures and how it is constructed — never the integrity, competence, or honesty of Cotality, Domain, or any person; both publishers are stated to compute their figures correctly and to publish their assumptions openly, and no individual is named. Politically neutral: housing affordability is a charged subject; AU-11 decomposes two publishers' figures as measurement objects, takes no position on housing policy, attributes the level of prices, incomes, or timeframes to no party or policy, and offers no view on whether any saving timeframe is desirable — the static-price point is presented strictly as a property of the models' arithmetic. Metric-identity held: a model output is kept distinct from a measurement, one household from a dual-income couple, gross income from post-tax income, the median dwelling from an entry-level dwelling, and a national figure from a city figure, in every sentence, caption, and label. Reference-period precise: every figure carries its publisher and release date. ASIC-clear: deposit-timeframe, price, and income data are general housing and economic information, not a financial product; the brief cites no security and gives no investment, property, mortgage, or savings advice.
Both sources are publicly available publisher reports, fetched live 2026-05-21. Cotality was formerly named CoreLogic; the report is published under the Cotality name. Full citations and the verified figures behind every number in this brief are listed in the companion FACTS.md, § H.