Quasi-Experiments in Health and Environmental Economics

本项目利用准实验产生的外生变异来分离卫生经济学中一些重要的关系。研究了以下两个广泛的问题：收入对死亡率的影响是什么？跨越多个学科的大量文献已经证实，收入较低的人健康状况较差，死亡率较高。然而，很难将收入作为这种关系的因果因素。该项目使用社会保障中经常被称为“福利缺口”的东西作为老年人收入变化的外生来源。考虑到福利金的迅速增加，1977年，联邦政府改变了新受益人的福利金计算方式，大幅减少了1916年12月31日以后出生的人的福利金。由于这些变化，两个有着相同生活经历但出生日期不同的人会得到非常不同的退休收入。该项目计划比较1916年最后一个季度和1917年第一季度出生的人的死亡率。如果收入确实影响死亡率，那么每月福利较低的人的死亡率应该更高。缺口实验是检验收入/死亡率关系的绝佳机会，原因有四。首先，这些福利大大减少了月供。第二，受影响群体的死亡率相对较高，因此更容易发现收入对死亡率的影响（如果存在影响的话）。第三，联邦政府经常改变老年人的收入，因此，如果收入对死亡率产生因果关系，可能会产生重要的政策影响。第四，对于狭义定义的队列，缺口福利似乎接近随机分配，因为在建立福利差异的立法通过之前，在缺口之前和之后出生的工人具有相同的观察特征。产前护理的好处是什么？虽然很容易确定产前检查次数多的妇女分娩结果更好，但很难将所有这些差异归因于产前护理。本来可以顺利怀孕的妇女（例如已婚、年龄较大、受教育程度较高的母亲）使用产前护理的比例也最高。由于潜在的遗漏变量偏差，构建一个能够伪造或证实护理与结果之间联系的令人信服的测试已被证明是困难的。本研究计划使用实地变化的产前护理访问，以隔离产前护理的好处。黑人妇女和城市居民严重依赖公共交通前往医疗机构。因此，在获得交通工具方面的冲击可以用作隔离产前护理减少的影响的一种方法。许多可能的准实验可以用于这方面，包括阿勒格尼县（匹兹堡）和费城的公共交通罢工。来自匹兹堡的初步证据表明，在罢工期间怀孕的妇女比其他时间怀孕的妇女接受产前护理的次数要少得多。如果产前护理改善了分娩结果，那么罢工造成的就诊减少应该会产生更糟糕的分娩结果。

This project uses exogenous variation generated by quasi experiments to isolate some important relationships in health economics. The following two broad questions are examined:What is the impact of income on mortality? A large body of literature that spans many disciplines has established that those with lower incomes have poorer health outcomes and higher mortality rates. However it has been difficult isolating income as the causal element in this relationship. This project uses what is frequently termed the "benefits notch" in Social Security as an exogenous source of variation in the income for the elderly. Concerned with rapidly increasing benefit payments, in 1977, the Federal government changed the way benefits were calculated for new beneficiaries, substantially decreasing payments for recipients born after December 31, 1916. As a result of these changes, two people with identical life histories but different birth dates would receive very different retirement incomes. The project plans to compare mortality rates for people born in the last quarter of 1916 and the first quarter of 1917. If income does impact mortality, there should be elevated death rates among those with lower monthly benefits. The notch experiment is an excellent opportunity to examine the income/mortality link for four reasons. First, the benefits notch reduced monthly payments by a substantial amount. Second, mortality rates in the impacted groups are relatively high, making it easier to detect an impact of income on mortality if one exists. Third, the incomes of the elderly are routinely changed by the Federal government and subsequently, there may be important policy implications if income causally impacts mortality. Fourth, for narrowly defined cohorts, the notch benefits appear to be close to randomly assigned in that workers born just before and after the notch had identical observed characteristics prior to the passage of the legislation establishing benefit differences.What are the benefits of prenatal care? While it is easy to establish that women with more prenatal care visits have better birth outcomes, it is hard to attribute all of these differences to prenatal care. Women who would otherwise have an uneventful pregnancy (married, older, more educated mothers, for example) also have the highest prenatal care use. Because of the potential omitted variables bias, constructing a convincing test that can falsify or confirm the link between care and outcomes has proven to be difficult. This research program uses field variation in prenatal care visits to isolate the benefits of prenatal care. Black women and city residents rely heavily on public transportation to get to health care providers. Shocks in the access to transportation can therefore be used as a way to isolate the impact of reduced prenatal care. A number of possible quasi experiments can be used in this context including public transportation strikes in Allegheny County (Pittsburgh) and Philadelphia. Preliminary evidence from Pittsburgh suggests that women pregnant at the time of the strike had substantially lower prenatal care visits than women pregnant at other times. If prenatal care improves birth outcomes, then the reduction in visits generated by strikes should produce worse birth outcomes.