The concept of anticipation and change, which underlie the principles of supply and demand, substitution, balance, and externalities, are basic to the sales comparison approach. Guided by these principles, an appraiser attempts to consider all issues relevant to the valuation problem in a manner that is consistent and reflects local market conditions.
　　依据供求原则、替代原则、平衡原则和外部性原则的预期的概念和变化的概念是市场途径的基础。在这些原则的指导下，评估师应竭力坚持以一致的方式判断所有与评估课题有关的事项，并反映当地的市场状况。
　　
　　Supply and Demand
　　Property price results from negotiations between buyers and seller. Buyers constitute market demand, and the properties offered for sale make up the supply. This assumes a market with many buyers and sellers acting in their own interests. To estimate demand, appraisers consider the number of potential users of a particular type of property, their purchasing power, and their tastes and preference. To analyze supply, appraisers focus on existing unsold properties as well as properties that are being constructed, or planned.供求原则
　　资产的价格是由买卖双方的洽商所决定的。购买者构成了市场需求，提供给市场销售的资产则构成了供给。在这里，我们假设市场上有很多买方和卖方，他们追求各自的利益。评估师为预测需求，需要考虑某一特定资产的潜在使用者的数量、他们的购买力以及他们的鉴别能力和偏好。为分析供给，评估师需要关注现在未出售的资产以及正在建造、生产或计划建造、生产的资产。
　　
　　Substitution
　　The principle of substitution holds that value of a property tends to be set by the price that would be paid to acquire a substitute property of similar utility and desirability within a reasonable amount of time. This Principle implies that the reliability of the sales comparison approach is diminished if substitute properties are not available in the market.替代原则
　　替代原则是指在合理的时间段内，资产的价值可由购买具有相似功能和满意程度的替代资产所支付的价格决定。这一原则意味着如果在市场上无可替代资产的信息，市场途径的可靠性就削弱了。
　　Balance
　　The forces of supply and demand tend toward equilibrium, or balance, in the market, but absolute equilibrium is almost never attained. Due to shifts in population, purchasing power, and consumer tastes and preferences, demand varies greatly over time. The construction of new buildings, and the demolition of old buildings cause supply to vary as well.平衡原则
　　供求力量的相互作用会使市场趋于均衡或平衡，但市场绝对的均衡几乎从未达到过。由于人口、购买力、消费者鉴别能力和偏好的变化，在不同时期内需求变化将很大。如新建筑的建设和旧建筑的损坏也会导致供给的变化。
　　
　　Externalities
　　Positive and negative external forces affect all types of property. Periods of economic development and economic depression influence property value. An appraiser analyzes the market area of the subject property to identify all significant external influences. To a great extent, the adjustments made for location reflect these external forces. Two competitive properties with identical physical characteristics may have quite different market values if one of the properties has less attractive surrounding.外部性原则
　　正面或负面的外部性因素影响着所有类型的资产。经济发展和经济衰退的周期影响着资产的价值。评估师需要分析评估标的所在的市场区域，以发现所有重要的外部影响。根据资产位置所进行的调整在很大程度上反映了这些客观的外部因素。两个物理特征相同的竞争性资产，如果其中一个周边环境不理想，它们的市场价值可能会有很大不同。
　　
　　本期词汇
　　Appraisal Principles评估原则，评估原理
　　指评估学中支持评估基本概念和方法的经济学理论或原则，是评估学的重要组成部分。通常包括预期原则(Anticipation)、变化原则(Change)、供求原则(Supply and Demand)、替代原则(Substitution)、平衡原则(Balance)等。在研究和学习评估方法等过程中，不能仅关注评估方法和程序、操作技巧方面的问题，首先要关注支持某一评估方法和概念的经济学原理。如支持市场法的评估原则就有预期和变化原则、供求原则、替代原则、平衡原则和客观性原则。
　　（主持人：王诚军）