Negative and zero time preference for health
研究发现多数人对健康有正时间偏好，但相当一部分人表现出负或零时间偏好，且感知健康严重程度、性别、教育及问题难度感知影响正偏好的概率。
The assumption of positive time preference is seldom challenged in analyses of intertemporal choices, despite considerable evidence of zero and negative discount rates. In this study, the majority of respondents have positive discount rates, but a substantial number have negative or zero discount rates. Using probit regression, the perception of the severity of the health-state, gender, education and perception of the questions in terms of difficulty are shown to influence whether individuals have positive discount rates.