BONS-全球房价负担能力调查2018（英文）-2017.12-67页-2mb

14th Annual Demographia International Housing Affordability Survey: 2018 Summary

Core Content

This document provides an analysis of housing affordability in the UK, based on the 14th Annual Demographia International Housing Affordability Survey using data from the third quarter of 2017. The study explores the effectiveness of the "median multiple" (MM) as a measure of housing affordability and evaluates its performance in different urban areas, while also considering the impact of house size, income distribution, and taxation on affordability.

Main Points

1. Housing Affordability and Asset Value Paradox

• Housing is both an asset and a service, leading to a paradox where the interests of current homeowners conflict with those of potential buyers.
• The UK housing market is dominated by homeowners, and housing is the most valuable asset, accounting for 62% of the country's total net worth by 2015.
• Despite rising house prices, there is a real affordability crisis, especially for lower-income groups.

2. The Median Multiple Method

• Demographia's median multiple method is a widely used benchmark for housing affordability.
• The method links median house prices to median household incomes and is considered the best available for international comparison.
• The correlation between the authors' replication of the MM and Demographia's is 0.92, indicating strong consistency.

3. Housing Market Boundaries

• The study highlights the importance of defining housing markets accurately, using functional urban regions (TTWAs) rather than administrative regions.
• Administrative regions (e.g., counties) often do not align with actual housing market areas, leading to variability in affordability within regions.
• For example, in the London Exurbs, there are 12 TTWAs, with affordability ranging from 4.6 to 7.8.

4. Impact of House Size on Affordability

• Adjusting for house size had a limited effect on affordability measures.
• The correlation between the size-adjusted MM and the original MM is 0.98, showing strong alignment.
• The median house size in the UK is relatively small (83.9 m²), but the difference in size across markets is not as significant as the differences in affordability.
• In some cases, adjusting for size even improved affordability, such as in Burnley, Lancashire.

5. Affordability Across Income Groups

• Affordability varies significantly across different income percentiles.
• Lower-income households face much higher affordability challenges.
• For instance, in London, the affordability ratio for the bottom 25th percentile is 10.3, while it is 7.8 for the top 25th percentile.
• In contrast, in Liverpool & Merseyside, the after-tax affordability gap reverses, showing that tax and benefits can significantly affect the affordability experience.

6. Tax and Benefits Consideration

• Pre-tax and post-tax affordability measures differ significantly.
• Adjusting for taxes and national insurance reduces the affordability gap, particularly in less affordable cities.
• In some cases, the gap disappears entirely, indicating that the MM measure is influenced by these factors.

Key Findings

• Replication Success: The authors were able to replicate Demographia's median multiple figures with a high degree of accuracy, suggesting the MM is a reliable and useful tool.
• Regional Variability: Administrative regions often contain a wide range of affordability within them, highlighting the need for more precise market definitions.
• Limited Size Adjustment Impact: Adjusting for house size has a small effect on affordability measures, as demand for space increases with income.
• Income Distribution: Lower-income households face significantly higher housing costs, even when purchasing smaller homes.
• Taxation Influence: Considering taxes and benefits can dramatically change the affordability picture, especially in highly unaffordable areas.

Conclusion

The study reinforces the value of the median multiple as a proxy for housing affordability, despite its limitations. It suggests that while the MM is not perfect, it remains a useful and effective measure. The authors emphasize the need for more accurate definitions of housing markets and the importance of considering income distribution and taxation when evaluating affordability. The findings also highlight the role of urban containment policies in exacerbating housing affordability issues and the necessity of addressing them to restore housing affordability and improve the standard of living.