【F1】The concept of life expectancy at birth is well understood by most people: the average age in which babies bom today will di

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问题    【F1】The concept of life expectancy at birth is well understood by most people: the average age in which babies bom today will die if death rates throughout their life course resemble those today. We have known for decades that in the U.S., on average, women live longer than men; whites live longer than blacks; and the rich and well educated live longer than those with low socioeconomic status.
   【F2】What we are only recently beginning to understand, however, is that educational attainment is becoming the single most important social determinant of longevity in America. The new research shows that college-educated white women are expected to live 9.3 years longer than their low-educated counterparts—those who have not completed high school—compared with only a 2.5-year difference in 1990.
   Variation is perhaps the second most important measure in statistics—the first being the average— summarizing the extent to which observations are spread around the average. 【F3】For example, we can observe two populations with identical life expectancy, but, from an individual perspective, the one with larger variation in life spans will have greater uncertainty in the age of death. If life span variation is very small, most deaths are concentrated close to the average; if variation is large, some individuals will die prematurely, whereas others will survive to a very old age.
   To put it concretely, if you had to bet on how long you will live, your best bet would depend more than anything else on your educational attainment. 【F4】Although betting on how long we will live may seem like an odd endeavor, this is precisely what we do, whether implicitly or explicitly, when we make decisions throughout the course of our life.
   Variation in life spans also affects the social and economic institutions planning for our old age, including the Social Security Administration and programs like Medicare. They too have to balance between contributions and benefits in an era of growing uncertainty about how long we will live. Perhaps more fundamental, the growing inequality in life spans—both in average and in variability—raises questions concerning distributive justice. 【F5】For example, if those at the lower rungs of the socioeconomic ladder are less likely to survive to old age—and, importantly, face greater uncertainty about their chances of survival—should we institute a differential retirement age? And what would such a scheme look like?
【F2】

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答案然而,我们最近才开始发现,在美国,受教育程度正成为长寿唯一的且最重要的社会决定性因素。

解析 ①本句是包含一个主语从句和一个表语从句的复合句。主干为主系表结构,主语为what引导的从句,what充当从句的宾语。②that引导的表语从句为主谓宾结构;the single…social为前置定语,of longevity为后置定语,均修饰宾语determinant,说明determinant的特点;in America为地点状语。
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