受訪金額在開放選擇條件評估支付模式的作用──引導或是誤導

Effect of the Proffered-price in the Combination of Discrete-choice and Open-ended Type Contingent Valuation Experiment: Directing Or Misleading

本文的研究目的首先將釐清開放雙界二元選擇詢價模式下之願付價格偏誤之成分，以做為建立偏誤校正模型之理論基礎，進而，則依此建構一個可供檢定及校正偏誤的結合模型，最後，乃比較由開放雙界二元選擇詢價模式中之開放欄位，及經由此一偏誤結合之檢定與校正模式所估計之效益差異，以能確知加入開放填答在二元選擇之後的詢價模式，對於前述相關偏誤呈現之影響。而本文用來驗證的資料，即是一套使用開放雙界二元選擇的詢價模式，評估墾丁國家公園資源經濟效益的調查資料。實證結果顯示本文建構的校正模型除了對於相關偏誤的內涵有更完整的詮釋外，利用此一詮釋亦得以檢定受訪金額在開放選擇模型中所扮演的角色，由各校正模型所估算出的平均願付價格之比較發現，開放選擇模型下所估算出之平均願付價格，明顯低於結合校正模型之估算值，顯示在開放雙界二元選擇模式下之開放欄位，該資料存在著向下修正的起始點偏誤，即結合開放與選擇雙界選擇模式中仍不能避免發生起始點偏誤，然而，此種詢價模式因為最後由受訪者填入一個確切的願付價格金額，如此將使得可能衍生的趨同回覆偏誤受到抑制。如此乃顯示結合開放與選擇雙界選擇模式的設計，是可以降低趨同回覆偏誤的支付方式。

The purpose of this paper is to clarify the components of the biases relating to the proffered-price in double-bounded dichotomous choice with open-ended followed up contingent valuation experiment. A testing and bias correction framework will then be constructed accordingly. Comparison of the mean willingness to pay from the open-ended responses and the corrected double-bounded dichotomous with open-ended elicitation answers is made to identify the effect of the bias from the combination of discrete and open-ended elicitation format. A set of data for the empirical demonstration is the benefit evaluation of Kenting national park in Taiwan. The empirical results have shown that the bias corrected model constructed in this paper has relatively complete explanation for the starting point bias, yes-saying bias, and all that in relation to the proffered price. Although the mean willingness to pay estimated from the final response of double-bounded dichotomous with open-ended elicitation framework exists downward starting point bias the yes-saying bias will be restrained from this type of elicitation method. It indicates that the double-bounded dichotomous with open-ended contingent valuation experiment is an elicitation method to suppress the occurrence of the yes-saying bias.