The data were collected at the 16th Annual Twins Day Festival in Twinsburg, Ohio, in August 1991. 495 adult twins were interviewed. The original study aimed to investigate 'By how much will another year of schooling most likely raise one's income?' Pairs of twins provide a control on confounding factors such as intelligence, family background, etc.
twins183 obs. of 16 variables:
the difference (twin 1 minus twin 2) in the logarithm of hourly wage, given in dollars.
the difference (twin 1 minus twin 2) in self-reported education, given in years.
Age in years of twin 1.
AGE squared.
Hourly wage of twin 2.
1 if twin 2 is white, 0 otherwise.
1 if twin 2 is male, 0 otherwise.
Self-reported education (in years) of twin 2.
Hourly wage of twin 1.
1 if twin 1 is white, 0 otherwise.
1 if twin 1 is male, 0 otherwise.
Self-reported education (in years) of twin 1.
the difference (twin 1 minus twin 2) in cross-reported education.
the difference (twin 1 minus twin 2) in tenure, or number of years at current job.
the difference (twin 1 minus twin 2) in marital status, where 1 signifies "married" and 0 signifies "unmarried".
the difference (twin 1 minus twin 2) in union coverage, where 1 signifies "covered" and 0 "uncovered".
Ashenfelter, Orley and Krueger, Alan. "Estimates of the Economic Return to Schooling from a New Sample of Twins." The American Economic Review 84.5 (Dec. 1994) 1157-1173.