Je ne regrette rien? Present-Bias and Time-Inconsistent Health and Retirement Decisions

本研究的目的是探讨当生命长度有限且内生时，双曲线贴现和时间不一致的生命周期选择对健康行为、健康结果和个人福利的影响。在内生健康和长寿的生命周期模型中，双曲线贴现对健康行为和寿命的作用在很大程度上还没有被探索，尽管这一问题在经验健康经济学和医学科学中引起了极大的关注。为数不多的几项经济学研究的一个共同特点是，它们忽视了健康行为影响寿命的事实。我们认为，实际上，戒除或减少不健康行为(如暴饮暴食或吸烟)的一个主要动机是考虑到这种行为造成的潜在健康缺陷和疾病及其对过早死亡的影响。香烟包装上的广告警告说：“吸烟致死”，并附有令人厌恶的吸烟导致健康缺陷的图片。因此，可以合理地假设，个人知道吸烟会降低他们的预期寿命，对长寿的渴望会影响不健康商品的消费决定，例如戒烟计划。挑战是解释为什么在当前的选择中没有充分考虑关于健康后果的知识，以及政策如何推动个人采取更健康的行为、更长寿、更少对过去的决定后悔。在拟议的项目中，我们将时间不一致的决策集成到健康赤字模型中，并调查了标准健康经济学理论无法解释的三种现象。1)我们调查了退休决策，并建立了一个理论来解释为什么个人比计划提前退休，尽管他们为退休存的钱比计划的少。原因将是他们未能坚持自己的健康计划(消费了比计划更多的不健康食物，未能戒烟等)，导致他们的健康和剩余预期寿命比计划更快地恶化。我们调查了政策如何推动个人坚持他们的健康和退休计划。2)当生命长度是有限的、内生的、决策是时间不一致的时，我们重新评估了成瘾的经济学理论。我们发展了一种理论，解释了为什么个人对自己的上瘾感到后悔，但无法摆脱上瘾，并讨论了防止上瘾发展和帮助个人克服上瘾的政策。3)我们发展了一个新的理论，为什么个人在预防性卫生保健(如癌症筛查或疫苗接种)上投入太少，并在感染疾病后后悔自己的行为。我们讨论了推动个人福利最大化预防性医疗保健需求的政策。

The objective of the proposed research project is to investigate the impact of hyperbolic discounting and time-inconsistent life cycle choices on health behavior, health outcomes, and individual welfare when the length of life is finite and endogenous. The role of hyperbolic discounting for health behavior and longevity remained largely unexplored in life cycle models of endogenous health and longevity although the issue attracts great attention in empirical health economics as well as in the medical sciences. A common feature of the few available economic studies is that they ignore the fact that health behavior affects the length of life. We argue that, actually, a major motivation of abstaining from or reducing unhealthy behavior (such as overeating or smoking) is the consideration of the potential health deficits and diseases caused by the behavior and their impact on premature death. ``Smoking kills'' warns the advertisement on cigarette packages, accompanied with disgusting pictures of smoking induced health deficits. It is thus reasonable to assume that individuals know that smoking reduces their life expectancy and that the desire for a long life influences the consumption decision of unhealthy goods, as for example the plan to quit smoking. The challenge is to explain why the knowledge about health consequences is insufficiently taken into account in current choices and how policy could nudge individuals to healthier behavior, a longer life, and less regret of past decisions.In the proposed project we integrate time-inconsistent decision making into the health deficit model and investigate 3 phenomena that cannot be explained by standard health economic theory. 1) We investigate the retirement decision and build a theory that explains why individuals retire earlier than planned although they saved less for retirement than planned. The reason will be that they failed to stick to their health plans (consumed more unhealthy food than planned, failed to give up smoking etc) such that their health and remaining life expectancy deteriorated faster than planned. We investigate how policy can nudge individuals to stick to their health and retirement plans. 2) We re-assess the economic theory of addiction when life length is finite and endogenous and decisions are time-inconsistent. We develop a theory that explains why individuals regret their addiction but are unable to escape addiction and discuss policies that prevent the development of addictions and help individuals to overcome addictions. 3) We develop a new theory why individuals invest too little in preventive health care (such as cancer screening or vaccination) and regret their behavior after they contracted a disease. We discuss policies that nudge individuals towards welfare maximizing demand of preventive health care.