Returns to education: What do twin studies control?

Kevin C. Stanek, William G. Iacono, Matt McGue

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The current article examines the assumptions of the MZ co-twin control method that has been applied in attempts to gain more accurate estimates of the returns to education by naturally 'controlling' for individual differences on which MZ twins are matched. The current study examined 1738 MZ and 926 DZ twins from Minnesota, including 133 pairs of MZ and 101 pairs of DZ twins discordant for university attendance. They were assessed prospectively on personality, intelligence, GPA, and academic motivation; a subset also has reported income at age 29. MZ twins discordant for university attendance differed significantly and prospectively on verbal IQ, personality traits, and GPA. While MZ co-twin control studies can provide more accurate estimates of the returns to education than analyses of single individuals, these studies do not entirely obviate the need to control for differences between university students and non-students that predate university attendance and might account for income differentials and even non-monetary outcomes.

Original languageEnglish (US)
Pages (from-to)509-515
Number of pages7
JournalTwin Research and Human Genetics
Issue number6
StatePublished - Dec 2011

Bibliographical note

Funding Information:
Supported by USPHS Grants # DA05147 and AA009367.


  • co-twin control method
  • discordant twins
  • income
  • returns to education

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