不動產估價最終估值之形成－－權重模式、估價偏誤與市場景氣之影響

The formation of final value of real estate appraisal: Weight model, appraisal bias and real estate cycle

不動產估價一般需採比較法、收益法及成本法等三種方法查估，比較法則需採三件比較標的推估，於最終估值形成通常仰賴權重的關連。內部權重方面，本文以2007年及2008年地價基準地6,435筆買賣實例建構特徵權重模型，發現比較法買賣實例權重受價格型態、交易日期接近性、是否屬近鄰地區、實例差異百分率絕對值加總、實例比較項目修正數、其他兩個實例相對值等自變數影響顯著。外部權重方面，本文將2,150筆三種估價方式權重建立聯立模型，以三階段最小帄方法（3SLS）進行估計。實證模型系統加權解釋力甚高，且三種方式權重之自變數多符合預期並顯著，顯見比較估值、收益估值與土地開發分析三種方式之關聯性。為探討成本法估值是否與成交價存在偏誤，以作為外部權重設定之基礎方面，本文以北部地區986筆交易案例，發現成本價格有高估之系統性偏誤現象，分量迴歸（quantile regression）分析實證認為成本法並未因屋齡較新之建物有較高精度。最後以2002年至2004年國內某金融機構對房屋貸款20,532件之估值，以二項式邏輯特（Binary Logit）模型分析。實證結果發現不景氣時期抵押貸款低估機率提高，景氣時期則無高估現象。

Real estate appraisal comprises the sales comparison, income, and cost approaches to value in general. This paper tries to assist quantifiable explanation when weighted average for three comparables in the Sales comparison approach and indicated values from three approaches are applied. For internal weight model, this paper examines the correlation between weight and internal attributes of 6,345 sales comparables from land value benchmark in 2007 and 2008 adopting the hedonic price model. The outcome shows the price type, the proximity of transaction date, inside the neighborhood area or not, total gross adjustment as %, numbers of adjustments, etc. are significant on the weight of comparables. For external weights, this paper builds a model based on the three-stage least squares method simultaneous equation (3SLS). The empirical result shows system weighted R2 is high and most attributes on the weights of three indication of value are significant and are consistent with expected sign. To explore whether the cost approach causes bias or not, and make it reference for establishment of external weight model, this paper compares the cost value, appraised by valuers applying the cost approach individually, from a sample of 986 transactions of properties sold in 2007 and 2008 in northern Taiwan, to sale price and finds the cost value is higher than sale price on average. With quantile regression, the outcome shows that the precision of cost value won't increase for newer buildings. Finally, this paper collects 20,532 mortgage appraisals from one bank from 2002 to 2004. With Binary Logit model, this paper finds the probability of lower appraisal is greater in bear market. The regression coefficients estimated from factors during the procedure of each approach could serve for reference if weighted average is applied reconciling the value conclusion by valuers.