模糊增加與共同保險需求之再探究

An Increase in Ambiguity and Demand for Coinsurance Revisited

本文章研究在淨財富分配不確定下，模糊增加提高共同保險需求之條件。有別於文獻研究決定該結果的條件僅適用於特定類別的模糊趨避者，本文章研究使所有風險趨避及弱模糊趨避（弱模糊愛好）者提高共同保險需求的決定性條件；而該決定性條件定義為可能的淨財富分配因為模糊增加所造成的改變。本研究發現，對於α-maxmin模型所描述的風險趨避及弱模糊趨避（弱模糊愛好）者而言，提高共同保險需求之決定性條件，為必須存在一個小於等於一之正數，使位置加權機率質點函數同時在最差（最好）及可能的淨財富平均分配下較大。此決定性條件的型態類似中央風險的減少。本文章進一步討論提高共同保險需求之模糊增加，對於在模糊下的期望效用的效果。

This paper investigates when an increase in ambiguity raises demand for coinsurance under uncertainty of a net-wealth (loss) distribution. Unlike previous papers that have studied the determining conditions limited to a specific class of ambiguity-averse individuals for ambiguity increases, this paper studies determining conditions characterized by changes in the possible net-wealth distributions resulting from an increase in ambiguity, for all risk- and weakly ambiguity-averse (risk-averse and weakly ambiguity-loving) individuals. When the preferences are characterized by an α -maxmin model, we find that, for risk- and weakly ambiguity-averse (risk-averse and weakly ambiguity-loving) individuals, the determining conditions involve a greater location-weighted probability mass function under both the worst (best) and possible net-wealth distributions on average for a positive scalar less than one, which are analogous to smaller central riskiness. We further discuss an effect of the increase in ambiguity raising the demand for coinsurance on expected utility under ambiguity.