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，双曲折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。在内源性健康和寿命的生命周期模型中，双曲折现对健康行为和寿命的作用在很大程度上尚未得到探索，尽管这个问题在经验卫生经济学和医学科学中引起了极大的关注。为数不多的经济研究的一个共同特点是，它们忽略了健康行为影响寿命的事实。我们认为，实际上，放弃或减少不健康行为（如暴饮暴食或吸烟）的主要动机是考虑到这些行为引起的潜在健康缺陷和疾病，以及它们对过早死亡的影响。香烟包装上的广告警告说：“吸烟有害健康”，并配以吸烟导致健康缺陷的恶心图片。因此，可以合理地假设，个人知道吸烟会缩短他们的预期寿命，并且希望长寿的愿望会影响不健康商品的消费决定，例如戒烟计划。挑战在于解释为什么在当前的选择中没有充分考虑到有关健康后果的知识，以及政策如何推动个人采取更健康的行为，延长寿命，减少对过去决定的遗憾。在本项目中，我们将时间不一致决策纳入健康赤字模型，并研究了标准健康经济学理论无法解释的3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，尽管他们的退休储蓄比计划少。原因是他们没能坚持自己的健康计划（吃了比计划更多的不健康食品，没能戒烟等），以至于他们的健康和剩余寿命比计划恶化得更快。我们调查政策如何能促使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理论。我们发展了一种理论，解释了为什么个人后悔自己的成瘾，但无法摆脱成瘾，并讨论了防止成瘾发展和帮助个人克服成瘾的政策。3)我们发展了一种新的理论，解释了为什么个人在预防性保健（如癌症筛查或疫苗接种）上投资太少，而在感染疾病后却后悔自己的行为。我们讨论的政策，推动个人向福利最大化预防保健的需求。

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.