twins {RbyExample}

Twins Income and Education Levels Data

Description

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.

Usage

twins

Format

183 obs. of 16 variables:

DLHRWAGE

the difference (twin 1 minus twin 2) in the logarithm of hourly wage, given in dollars.

DEDUC1

the difference (twin 1 minus twin 2) in self-reported education, given in years.

AGE

Age in years of twin 1.

AGESQ

AGE squared.

HRWAGEH

Hourly wage of twin 2.

WHITEH

1 if twin 2 is white, 0 otherwise.

MALEH

1 if twin 2 is male, 0 otherwise.

EDUCH

Self-reported education (in years) of twin 2.

HRWAGEL

Hourly wage of twin 1.

WHITEL

1 if twin 1 is white, 0 otherwise.

MALEL

1 if twin 1 is male, 0 otherwise.

EDUCL

Self-reported education (in years) of twin 1.

DEDUC2

the difference (twin 1 minus twin 2) in cross-reported education.

DTEN

the difference (twin 1 minus twin 2) in tenure, or number of years at current job.

DMARRIED

the difference (twin 1 minus twin 2) in marital status, where 1 signifies "married" and 0 signifies "unmarried".

DUNCOV

the difference (twin 1 minus twin 2) in union coverage, where 1 signifies "covered" and 0 "uncovered".

Note

There are 183 cases; 147 complete cases. Twin 1's cross-reported education is the number of years of schooling completed by twin 1 as reported by twin 2. For data analysis, the logarithm of the hourly wage is typically used instead of hourly wage.

Source

Guido Imbens, PhD. UCLA, Department of Economics.

References

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.