Linking studies to assess the life expectancy associated with eighth grade school achievement.

Extensive evidence indicates the causal association of school outcomes and long-term health. We combined the findings of two studies by Chetty and colleagues to estimate the life expectancy associated with achievement scores in the eighth grade. We linked the dependent variable of the first study and the independent variable of the second study. The first study (of students in Tennessee) found a positive correlation between school achievement scores in eighth grade and income at age 25-27. Controlling for family background, a one percentile increase in eighth grade test score was associated with an increase of $148 (95% CI: $125, $172) in 2009 $U.S. in mean yearly wages at ages 25-27 years. Based on estimated mean annual income growth of 3.35%, $148 would increase 1.59 fold to $235 (CI: $199, $273) in 14 years, at age 40-$251 (CI: $213, $292) in 2012 $U.S. adjusted for inflation. The second study (of the U.S. population) found that a one percentile household income ($1500 in 2012 $U.S.) was associated with one month life expectancy at age 40. We calculate that an increase in income at age 40 attributable to one percentile increase in eighth grade test scores, i.e., $251, would increase life expectancy by 17% (i.e., $251/$1500) (CI: 14%, 19%) of one month per percentile eighth grade test score. Estimates of long-term health outcomes associated with educational outcomes can be made with caution. Applicability of findings from the Tennessee to the U.S. population is discussed.