三要素混合模型於設限資料之願付價格分析

Abstract

在探討願付價格的條件評估法中一種常被使用的方法為“雙界二分選擇法”，並且一個隱含的假設是，所有研究對象皆願意支付一個合理的金額。然而對於某些商品，有些人也許願意支付任何金額；相對的，有些人可能不願意支付任何金額。分析願付價格時若不考慮這兩類極端反應者，則可能會得到一個偏誤的願付價格。本篇研究中，我們提出一個“混合模型”來處理此議題，其中以多元邏輯斯迴歸模型來描述不同反應者的比例，並以加速失敗時間模型來估計願意支付合理金額者其願付價格的分布。此外，我們以關於治療高血壓新藥之願付價格實例，作為實證分析。

One commonly used method in contingent valuation (CV) survey for WTP (willingness-to-pay) is the “double-bound dichotomous choice approach” and an implicit assumption is that all study subjects are willing to pay a reasonable price. However, for certain goods, some subjects may be willing to pay any price for them, while some others may be unwilling to pay any price. Without considering these two types of the extreme respondents, a wrongly estimated WTP value will be obtained. We propose a “mixture model” to handle the issues in this study, in which a multinomial logistic model is taken to specify the proportions of different respondents and an accelerated failure time model is utilized to describe the distribution of WTP price for subjects who are willing to pay a reasonable price. In addition, an empirical example on WTP prices for a new hypertension treatment is provided to illustrate the proposed methods.