Information from two data sources is used in the paper: The Swedish Twin
Registry and the 1991 wave of the Swedish Level of Living Survey (the SLLS).
The following variables are used from these two sources:

1.Annual Earnings in 1987, 1990 and 1993: Called SCB14, SCB31 and SCB48,
respectively in the twins data and i246, k50 and k727 in the SLLS.

2.Highest Attained Educational Level and Field of Study: Called SCB64 and
SCB63 in the twins data and K446 in the SLLS. 

3.Years of Schooling: Called Y131 in the SLLS.

4.Birthyear: Called BYEAR in the twins data and Y11 in the SLLS.

5.Sex: Called SEX in the twins data and Y10 in the SLLS 

6.Number for pair: Called PARNR in the twins data.

7.Indicator of twin number within each pair: Called TVAB in the twins data set 

8.Number for individuals: Called NUMMER in the twins data and Y1 in the SLLS.

9.Indicator of zygosity: Called ZYG in the twins data 

10.Age of Separation from Twin brother/sister: Called NYRA62 in the twins data.

11.Indicator of where the individual was born: Called Y19 in the SLLS.

The selection of observations, construction of variables and estimating
procedures used in the paper are presented in the file estim.sas, which was
originally written for use with the SAS software v.8.02 for PC. If you have
any questions regarding this file please send them to:

Gunnar Isacsson
VTI/TEK
Box 760
781 27 Borlange, Sweden
E-mail:gis@du.se