購租屋決策分析──實質選擇權的應用

Applying the Concept of Real Option to the Household Decision Making of Tenure Selection

本研究將實質選擇權的觀念應用到家計單位的購屋決策上，指出當未來的房價為不确定狀況，且租屋市場的存在同樣能滿足其住屋需求下，家計單位在考慮是否進行購屋決策時，其背後隱含一何時（timing）購屋的機會選擇，為一個遲延決策選擇權（defer option）的要領價值，并利用二項式選擇權評價模式（binomial option pricing model），實際推導此一選擇權的價值。使用本研究的模型架構進行分析，可以清楚的由數據進行投資決策之判斷，有助於家計單位正确評估購租屋決策。結果指出，當未來房價的波動性較大時，此一選擇權價值上升；當個人資金必要報酬率提高，會使得選擇權價值下降；當租金水準提高時，選擇權的價值亦提高。

This study applies the concept of real option to the household decision making of tenure selection. As the house price in the future remains uncertainty, tenure selection is like a timing option to buy a house. This study does not only indicate that this option is an American put option, but also derive the value of the put option through binomial option pricing model. On the one hand, if the household selects to pay the rent for one period instead of buying a house, the expenditure may be reimbursed due to the decrease of house price. On the other, the expenditure may rise due to the increase of house price. This study offers a useful model for household to determine whether it is a right decision to buy or rent a house. The result shows that the more volatile the house price, the higher the option value; the higher the ratio of equity to house price, the lower the option value.