台北市住房可負擔性–剩餘所得法分析

Abstract

摘要 台灣持續高漲的房價已成為了嚴重的社會問題，而這樣的現象於台北市尤為明顯。在所有房價相關議題中，住房可負擔性又與民眾最為切身相關。報章雜誌、新聞媒體、政府機關及學界經常出於計算簡便及易於理解而使用房價所得比作為住房可負擔性的衡量標準，隱含假設不論具備如何社經條件及人口特徵的家戶皆適用相同比例做為住房是否可負擔的基準，不僅忽略了住房可負擔問題的邏輯本質，也未考量除了購屋之外，以租屋形式消費住房也是主流住房方式的現實。 本文首先比較主流兩種住房可負擔性衡量方式的相對優劣，並以2015年台北市購屋及租屋市場作為釋例，發現相較剩餘所得法 (Residual Income Approach) 衡量住房可負擔性，以比例法 (Ratio Approach) 衡量住房可負擔性更容易得出誤導性結論。因此本文有別於傳統以比例法衡量住房可負擔性的文獻，結合近年逐漸獲重視且更有理論基礎的剩餘所得法及勞倫茲曲線的概念，並採用更完整且精確的內政部實價登錄資料，從最早的資料完整年份2013年開始，逐年比較和衡量2013年至2015年台北市整體及各所得水準，及2015年台北市各行政區及年齡層家戶的購屋及租屋可負擔性。最後，根據上述分析結果及衡量模型，本文也分析比較了各種政府政策對於購屋及租屋可負擔性的改善效果及成本效益關係。 本文發現，台北市存在嚴重且逐年惡化的購屋可負擔問題，而低所得分位家戶存在租屋可負擔問題，但租屋可負擔問題整體而言較為穩定，沒有逐年惡化的現象。此外，不同行政區的家戶面對的購屋與租屋可負擔問題程度差異甚大，且隨家戶戶長年齡增長，住房可負擔問題有逐漸改善的現象。最後，本文發現，延長優惠房貸還款年限對於整體購屋可負擔性改善效果明顯，但對於最低所得十分位的家戶而言沒有效果。此外，在包含購屋補貼、利率補貼以及租屋補貼三種補貼類型政策中，控制政府總支出的前提下租屋補貼的政策效益最佳，且採用排富條款不僅更能改善低所得水準家戶無法負擔購屋及租屋的問題，也有助於顯著加強政策的整體可負擔性改善效果。

Abstract The rise of house price in Taiwan has become one of the most serious social problems, and it is particularly true in Taipei. Among all the issues related to house price, housing affordability is the most consequential one in terms of the interest of the public at large. Media outlets, government agencies and scholars often apply the price-to-income ratio in the measurement of housing affordability due to its relative ease of calculation and being understood, implicitly assuming, in determining whether there is a housing affordability problem for a specific household, the same threshold price-to-income ratio apply to every household regardless of its economic, social and demographic conditions. This approach fails to recognize the logical essence of the housing affordability problem and the existence of house rental as an alternative. This paper starts by comparing the strengths and weaknesses of the two mainstream methods for evaluating housing affordability, using house purchasing and rental markets in Taipei in 2015 as an illustrative example. It is discovered that, compared to residual income approach, misleading conclusions are more likely to be drawn under ratio approach. Therefore, this paper combines the idea of Lorenz Curve and the residual income approach which is getting growingly more attention and backed by logic and theory to evaluate housing affordability in Taipei by income levels, methods for housing consumptions, years, districts and ages. Finally, based on the model developed in previous chapters, this paper calculates and compares the costs and benefits of each possible policy aimed at improving housing affordability. This paper discovers that purchase affordability problem in Taipei is serious and has been exacerbated as day goes by and even house rental is unaffordable for households with lower income, while rental affordability remains stable through the years. Besides, affordability varies greatly across different districts in Taipei and improves with the increase in age. Finally, this paper finds out extension of repayment period has significant effect on overall purchase affordability, but has no effect for households with the lowest income. In addition, among three subsidy policies, holding total government expenditure constant, rental expense subsidy has greater effect in improving housing affordability, and income limits clause helps not only improve the purchase and rental affordability for households with lower income, but also helps improve the overall rental affordability.