How large are the effects from changes in family environment? A study of Korean American adoptees

I analyze a new set of data on Korean American adoptees who were quasi-randomly assigned to adoptive families. I find large effects on adoptees' education, income, and health from assignment to parents with more education and from assignment to smaller families. Parental education and family size are significantly more correlated with adoptee outcomes than are parental income or neighborhood characteristics. Outcomes such as drinking, smoking, and the selectivity of college attended are more determined by nurture than is educational attainment. Using the standard behavioral genetics variance decomposition, I find that shared family environment explains 14 percent of the variation in educational attainment, 35 percent of the variation in college selectivity, and 33 percent of the variation in drinking behavior.