Other ways to measure housing affordability 

Housing affordability is about the ability to balance housing costs with available household financial resources so that individuals, families and whānau have enough income left over to pay for other necessities. 

A variety of approaches are used based on conceptual and practical considerations.  

Which measure is best suited for my purpose? 

Different data sets and measures suit different specific research questions. 

If you’re seeking to understand housing affordability through a place-based lens then census data and the CHAI are suitable. The CHAI are also the most timely measures available. 

To access demographic breakdowns of housing affordability, the Household Economic Survey (overburden rates or residual income) and census are most suitable, but less timely than the CHAI. 

 A visual diagram explaining which resource is best for specific research questions, as described in the text above.

A summary of New Zealand’s housing affordability statistics 






Price-to-income ratios 



Shows aggregate association between prices and incomes, over time and places. 

Lacks distributional information (e.g. who has/does not have access to affordable housing). 


Wide choice of data sources mean results can differ. 


Do not include housing quality, nor account for borrowing costs (except CHAI) 

Ubiquitous reports comparing aggregate income to house price and rental costs:  


Stats NZ’s(external link) income, housing costs, and price data (Household Economic Survey - income and housing costs; Rental Price Index; Census - rent to income; example comparisons in Housing in Aotearoa 2020 report). 


HUD’s Change in Housing Affordability Indicators (CHAI) includes mortgage serviceability and quality-adjusted price changes. 






High frequency 

Proportion of income on housing costs (‘overburden rates’) 

Intuitive; easy to explain.  


Household level metric, so can be aggregated by demographic groups. 


Widely used internationally so can be used for benchmarking. 

Threshold is arbitrary (30% + of income on housing costs is common rule-of-thumb) 


Higher income households may be able to afford higher proportions (choose to consume more housing) 


Stats NZ’s(external link) proportion of households spending more than 30 percent of disposable (after-tax) income on housing costs (from Household Economic Survey - HES). 


DPMC(external link) Child Poverty Related Indicators (from HES). 


OECD(external link) – cost overburden among low-income: tenants (private rent); owners with mortgage. 






Residual income 

Shows income after housing-costs 


Useful to identify those at-risk of financial hardship 

Minimum income threshold is arbitrary 


Can misdiagnose general cost-of-living problems as cost-of-housing problems 



HES:(external link) Low-residual income after housing costs (aka (‘shelter poverty’). 


HES(external link): Disposable income before and after housing costs, by income distribution and inequality measures (e.g. P90/P10 and Gini coefficient). 


Stats NZ's(external link)  Child poverty statistics show before/after housing costs poverty rates (housing costs induced poverty rates can be derived), by region and ethnicity. 





Ethnicity (incl. Māori) 


Subjective indicators 

Complements other measures of housing outcomes 

Perceptions may differ across individuals and over time 

General Social Survey.(external link) 



Iposs NZ Issues Monitor.(external link) 

Ethnicity (including. Māori) 


Ethnicity (including. Māori) Household composition 



Disability status 

Migrant status 





Housing quality 

A related dimension to consider alongside affordability metrics. 

Housing quality is hard to define and changes over time 

HES: (external link) Cold, mould or damp, including by income quintile. 


GSS:(external link) Cold, mould, damp, repairs/maintenance needed. 


Overcrowding: HES and Census. (external link)

Ethnicity (incl. Māori), Age, Sex, Region