Abstract Article history: Received 3 January 2011 Accepted 14 February 2011 Keywords: real estate Appraisal; sales comparison approach; reconciliation; correlation; weight of appraisal; appraisal bias; underestimation in bear market Corresponding author: Shih-Ming You E-mail address: moi0884@moi.gov.tw 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.