建物價值隨時間經過而降低，提列該折舊的方式，便宜行事下多採定額法，且規定一定數額之「殘價率」，此論點之適當性小則影響房屋稅捐多寡、大則影響民眾於都市更新中之權益。然過去相關研究中，有論證凸型折舊者、也有主張凹型折舊者。本文以高雄市透天住宅之建物價格為對象，參考修正Cannaday and Sunderman（1986）對屋齡與價格關係之衡量方式，證實建物折舊呈現凸型；進而以該型態設置迴歸模型，分析屋齡效果。研究結果顯示，各行政區之屋齡效果具顯著差異，剩餘價值普遍較殘餘價值高。以此推論，於房屋課稅或不動產估價師執行估價，採齊一式線型規範的方式，恐無法反應實際之剩餘價值，而可能損及民眾權益。
Building value decreases because of physical deterioration over time. The most popular method for estimation of depreciation is straight-line method. However, some empirical studies show it is concave, and some literatures illustrate convex depreciation. In this paper, we use real building price database from Kaohsiung City and use a log-linear model to test the path of depreciation. The result supports a convex path of building depreciation and residual value is higher than scrap value.We suggest that ”straight-line rate method” and ”sum of the year digits method” are better to apply on building depreciation in Kaohsiung City. Legally-specified rate should be amended.
