Ratio between greenfield and infill housing construction in Sydney over the last 40 years

- John Muscat 

The NSW Government is doubling down on densification as if, according to the rhetoric, it is an untried solution to Sydney’s housing affordability problem. But an engineered shift from greenfield to infill has been going on for decades. Under the current policy consensus few are asking whether this shift is itself part of the problem. A question like this needs to be considered a in historical context. AI can be useful in gaining a handle on data intensive urban and housing development issues as long as the results are corroborated by consulting original sources. With that qualification in mind, the information below is extracted from the Grok AI answer to the following question: “How has the ratio between greenfield as opposed to infill housing construction changed in Sydney Australia over the last 40 years”.

Key Policy and Trend Shifts

• 1980s–Early 1990s: Greenfield Dominance: Rapid population growth and fewer restrictions led to substantial greenfield expansion on Sydney's outskirts. Historical estimates suggest greenfield accounted for 60–75% of new supply, driven by demand for detached housing. Infill was minimal (under 30%), limited to opportunistic brownfield sites (e.g., former industrial land).
• Mid-1990s–2010s: Policy Push for Infill: Post-1990s reforms (e.g., urban consolidation strategies under NSW planning laws) restricted greenfield via urban growth boundaries and land rationing, targeting 70% infill to 30% greenfield by the 2005–2031 Metropolitan Plan. This aligned with national trends, where infill rose from ~50% in the 1990s to 60–70% nationally by the 2010s. In Sydney, infill approvals grew with apartment booms in areas like Parramatta and Liverpool, though actual delivery lagged targets due to higher infill costs (10–30% more than greenfield per dwelling).
• 2010s–2020s: Mixed Delivery, Recent Greenfield Resurgence: Despite targets, infill hit hurdles like zoning delays and NIMBYism. By 2017–18, greenfield was only ~18% of completions, implying ~82% infill. However, this shifted sharply: by 2022–23, greenfield rose to ~47% amid booming detached house demand and infill slowdowns (e.g., post-COVID backlogs). Transit-oriented infill (near stations) fell from 42% (2017–18) to 31% (2022–23). Projections under the 2018 Greater Sydney Region Plan maintain a 70:30 infill: greenfield target through 2036, but delivery risks undersupply if greenfield land depletes (e.g., North West Growth Areas nearing exhaustion).

Quantitative Trends in Ratios Direct 40-year time-series data is sparse, but pieced from government reports, ABS indicators, and planning dashboards, the ratio of greenfield to total new housing completions (greenfield / total) has trended as follows. Note: Ratios are approximate, based on dwelling approvals and completions; infill is the complement (total minus greenfield). Early estimates draw from national proxies adjusted for Sydney's fringe-heavy growth.

Period	Est. Greenfield Share	Est. Infill Share	Key Drivers/Notes
1985–1994	60–70%	30–40%	Greenfield-led sprawl; low infill due to limited zoning for density.
1995–2009	40–50%	50–60%	Post-1990s restrictions; infill rise via urban consolidation (e.g., 2005 Metro Plan targets).
2010–2016	25–35%	65–75%	Peak policy enforcement; apartment approvals surge (e.g., 11,000+ attached dwellings/year in Sydney).
2017–2021	~18–30%	~70–82%	Low greenfield amid high infill targets; COVID disrupts but boosts detached demand.
2022–2025	~40–47%	~53–60%	Greenfield rebound (47% in 2022–23); infill constrained by costs (e.g., $624k/unit vs. $595k greenfield house in 2010-adjusted terms).

Ratio Interpretation: The greenfield-to-infill ratio (greenfield: infill) declined from ~2:1 (1980s) to ~1:3 (mid-2010s), reflecting densification success. Recently, it rebounded to ~1:1 (2020s), signalling policy-market tension. Nationally, similar patterns hold: 60% infill target since 2010, but actuals hover at 50–60%.