While twin and adoption studies usually find that your family has a small effect on how far you get in school, exceptions exist. Some twin research reports that upbringing used to be more important and continues to be more important for women. An early study of Norwegian twins found strong family effects for female twins born before 1961, and male twins born before 1940. During the prewar era, if you had one extra year of education, you could expect your adopted sibling to have about six extra months. Researchers using the Minnesota Twin Family Registry and the Finnish Twin Cohort Study
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This implies more about high growth and massive educational expansion of boomers/gen x /millennials than it does fundamentals
