Table 2 Correlations for educational attainment are consistently higher between dizygotic twins than between non-twin siblings suggesting twin-specific shared environments influence this trait.

Gratz et al. (2021)⁸

Finland (1974–1980)

Registers (Statistics Finland)

0.36

0.52^a

Finland (1974–1979)

Finn16

Silventoinen et al. (2020)¹³

0.60^b

Finland (1936–1955)

Finnish Twin Cohort Study

Silventoinen et al. (2004)⁷⁶

0.62^b

Finland (1919–1957)

Finnish Twin Cohort Study

Silventoinen et al. (2000)⁷⁷

Germany (1976–1989)

SOEP

0.51

0.60^a

Germany (1990–1993)

TwinLife

Baier & Lang (2019)⁶⁰

0.60^a

Germany (1914–1969)

Bielefeld Longitudinal Study

Silventoinen et al. (2020)¹³

0.67^a

Germany (1926–1987)

Berlin Twin Register

Norway (1970–1980)

Registers

0.41

0.51^b

Norway (1967–1979)

Norwegian Twin Register

Ørstavik et al. (2014)⁷⁸

0.46

Norway (1967–1979)

Norwegian Twin Register

Lyngstad et al. (2017)⁷⁹

Sweden (1960–1982)

Multi-generation Registry

0.44

0.55

Sweden (1926–1958)

Swedish Twin Registry

Isacsson (1999)⁸⁰

0.50^c

Sweden (1950–1970)

Multi-generation Registry

Rietveld et al. (2013)³⁷

UK (1954–1989)

UKHLS

0.42

0.47

UK (1951–1985)

TwinsUK

Branigan et al. (2013)¹²

USA (1954–1986)

PSID

0.51

0.56

USA (1976–1984)

AddHealth

Nielsen & Roos (2015)¹⁸

0.52^a

USA (1908–1977)

California Twin Programme

Silventoinen et al. (2020)¹³

0.54^a

USA (1910–1976)

Carolina African American

0.56^a

USA (1979–1989)

Colorado Twin Registry

0.61^a

USA (1894–1987)

Mid Atlantic Twin Registry

0.39

0.49

Norway (1946-65)

Registers

Björklund & Salvanes (2011)⁶¹

0.45

0.50

Sweden (1950–1970)

Multi-generation Registry

Rietveld et al. (2013)³⁷

0.45

0.56

USA (1976–1984)

AddHealth

Nielsen & Roos (2015)¹⁸