What Do Twins Studies Reveal about the Economic Returns to Education? A Comparison of Australian and U.S. Findings
What Do Twins Studies Reveal about the Economic Returns to Education? A Comparison of Australian and U.S. Findings
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发表时间：
1995
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通讯作者：
P. Miller;C. Mulvey;N. Martin
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作者：
P. Miller;C. Mulvey;N. Martin
教育回报率的传统估计受到限制，因为它们无法将教育回报与个人能力的贡献和家庭背景的影响分开。使用双胞胎样本的研究可能会克服这些问题。同卵双胞胎在基因上是相同的，如果他们是一起长大的，那么他们就有着相同的家庭背景。因此，同卵双胞胎之间的收入差异可以与他们所接受的教育量的差异相关联，以便估计教育的独立影响。将这些估计值与从基因相似但不完全相同的双卵双胞胎样本中得出的估计值进行比较，可以评估传统教育回报估计值中与能力和家庭背景相关的偏差。在一篇重要的论文中，Jere Behrman等人（1977）分析了一对男性二战老兵双胞胎的样本数据，发现在8%的总体教育回报率中，2.7%可以归因于教育本身，3.2%可以归因于遗传因素，2.1%可以归因于共同的家庭环境。然而，在最近的一篇论文中，Orley Ashenfelter和Alan Krueger（1994）使用一个新的双胞胎样本的数据估计了教育的经济回报，这使得他们能够调整他们的估计，以忽略能力变量和测量误差。在此基础上，他们发现家庭和遗传效应对学校教育的回报几乎没有贡献。然而，测量误差使学校教育的估计回报率向下偏移。阿申费尔特和克鲁格（Ashenfelter and Krueger，1994）的研究结果与该领域以前的研究结果有很大不同，现在人们对双胞胎数据的分析真正揭示了教育的经济回报有一些困惑。Ashenfelter和Krueger的研究结果是基于对1991年参加双胞胎节的298人（149对同卵双胞胎）的数据分析。他们在论文的结尾处评论道：“只有收集更多的数据才有可能更好地估计学校教育的回报”（第1171页）。
Conventional estimates of rates of return to education are constrained because they are unable to isolate the returns to schooling from the contribution of individual ability and the influence of family background. Potentially, studies using a sample of twins may overcome these problems. Monozygotic twins are genetically identical and, if they have been reared together, share the same family background. Differences in income between identical twins can therefore be associated with differences in the amount of education they have undertaken, in order to estimate the independent influence of education. Comparisons of such estimates with estimates made from a sample of dizygotic twins, who are genetically similar but not identical, and who are also reared together, may permit evaluation of the biases associated with ability and family background in conventional estimates of the return to education. In an important paper, Jere Behrman et al. (1977) analyzed data from a sample of male World War II veteran twins and found that, of the overall rate of return to schooling of 8 percent, 2.7 percentage points, could be attributed to schooling per se, 3.2 percentage points could be attributed to genetic factors, and 2.1 percentage points could be attributed to shared family environment. In a recent paper, however, Orley Ashenfelter and Alan Krueger (1994) have estimated the economic returns to education using data on a new sample of twins which permitted them to adjust their estimate for omitted ability variables and measurement error. On this basis, they find that family and genetic effects make virtually no contribution to the returns to schooling. Measurement error, however, biases the estimated return to schooling downward. The findings of Ashenfelter and Krueger (1994) are very different from previous work in this field, and there is now some confusion as to what analysis of twins data really reveals about the economic returns to schooling. Ashenfelter and Krueger's results are based on analysis of data for a sample of 298 individuals (149 pairs of identical twins) who attended a twins festival in 1991. They remark at the end of their paper "Only additional data collection is likely to lead to better estimates of the returns to schooling" (p. 1171).