「口碑」是行銷領域的重要議題，過去許多有關口碑的研究都指出口碑對行銷的影響力。例如：Katz and Lazarsfeld(1955)指出口碑對消費者購買決策的影響力是報章雜誌的七倍、人員銷售的四倍，以及廣播的兩倍；Day(1971)的研究則認為口碑對消費者從厭惡態度轉為正面態度的影響力是廣告的九倍；Trusov et al.(2009)的研究也指出口碑在獲取網站客戶上較其他媒體有效三十倍。從這些例子我們知道口碑的重大影響力，也知道口碑的價值在不同的商品、市場與組織情境下會有不同(Ennew et al., 2000; Christiansen & Tax, 2000)。然而，針對這些口碑研究會出現不同口碑效果的這個問題，過去文獻卻鮮少有人探究。因此，本文依照經濟學彈性的原理，建構口碑彈性概念，並將概念落實於調查研究上加以詴算，藉此來衡量與比較口碑效果。 「彈性」(elasticity)的概念在經濟學領域被普遍使用，原因有二：第一、在學理上，我們可以很容易地用「彈性」連結兩個事件的因果關係； 第二、用彈性指標，我們可以清楚地比較與分析所研究產品的特性。因此本文是結合口碑行銷與彈性兩者，用以探討商品種類、口碑彈性與口碑效果之間的關連性，並以旅遊商品為研究標的，在台灣地區所進行的一項實證分析。 在本文的研究中，由於商品口碑不如商品價格容易衡量，因此在資料蒐集上，我們以消費者的口碑主觀評價來模擬口碑數量，藉以取得數值來進行「口碑彈性」的計算。在邏輯上，本文將口碑彈性當作一個影響銷售的中介變數，受到了除口碑以外的其他變數影響，從而整合了其他變數來探索與口碑效果之間的關係。在研究方法上，我們用Cobb-Douglas形式建構口碑銷售函數，再以迴歸模型求取各商品的口碑彈性值，作為本研究的結果，最後以研究結果進行後續的分析與討論。

Word-of Mouth (WOM) is an important issue in marketing. Numerous studies have demonstrated that WOM is an effective marketing tool, for example, Katz and Lazarsfeld (1955) concluded that the impact of WOM on consumer’s purchase decision is seven times than advertising, four times than personal selling and two times than broadcasting. Then, Day (1971) found that WOM is nine times more effective thanadvertising at converting unfavorable or neutral consumer attitudes into favorable attitudes. Trusov et al. (2009) pointed out that WOM in website member acquisition is 30 times higher than media appearances. These examples demonstrate the tremendous influence of WOM. Furthermore, the value of WOM varies across product, market, and organizational contexts (Ennew et al., 2000; Christiansen &Tax, 2000). However, the reason of the mixed results of these literatures has rarely been explored. Therefore, the study used the principle of economic elasticity theory to construct WOM elasticity concept and take this concept into practice to estimate the value of tourism products for measuring and comparing the WOM effect.
This study defined the concept of WOM elasticity (Ewomx), which can be generalized to quantify WOM effects and link both variables of WOM and product sales, in addition, WOM elasticity can help us to compare and classify the product category. Thus, this research combined elasticity theory and marketing research to discuss the relationship of product category, WOM elasticity and WOM effect. The research target in this study is tourism industry and the empirical analysis was conducted in Taiwan.
Disposing of restrictions on measuring WOM objectively, the author asked consumers to form their subjective evaluation of a product or service’s WOM to accurately assess their opinions and estimated Ewomx. In logic of this study, the WOM elasticity is an intermediate variable that can integrate all variables which affect product purchasing except WOM to determine the consumption. A simple econometric model is used to examine the result of WOM elasticity outcomes we concern. We set the WOM consumption function as a Cobb-Douglas type and get the final WOM elasticity value by passing through a simply regression model. The results and theoretical implications and future research issues are discussed.

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