st: sample selection problem in a discrete-time event history analysis(competing risks)

[Teresio Poggio <teresio.poggio@poste.it>]

Dear Statalisters,

I'm studying housing tenure at first marriage among Italian couples, 
using retrospective information collected from married women in a 
cross-sectional national survey.

I'm doing a discrete-time event history analysis for women and men, 
modeling competing risks for tenure of their first accomodation (home 
ownership, rent, rent free, cohabiting with parents) versus not marrying.
In practice, I'm using mlogit procedures (Stata 8; 9 is shipping) on a 
person-year data matrix, following the approach proposed by Allison (1982).

I have a sample selection problem as information on accomodation at 
first (or only) marriage was not collected in the survey for divorced 
people, widows and not married cohabiting partners. Nor for people that 
married twice or more.
The problem is related only to my dependent variable, housing tenure at 
first marriage. While information on year of the first marriage and 
relevant time-varying independent variables are available for all the 
records.

In short, my (women, for instance) sample is organized in this way:

a) 1,173 never married women
Included in the analysis (at "risk" of marriage)

b) 11,486 married women, both partners at their first marriage
Included in the analysis (outcome known)

c) 1,467 (total) divorced, widowed women and not married women,in couple
Excluded from the analysis because tenure at first marriage is unknown.

d) 124 married women, but not at their first marriage.
Excluded from the analysis because tenure at first marriage is unknown.

e) 143 married women, but their husbands are not at their first marriage
Excluded form the analysis for theoretical reasons and analytical 
simplicity

Simply discarding (c), (d) and (e) will result in seriously biased 
estimates. So I'm looking for a way to control for this selection.
Can anyone provide suggestions?

Best,

Teresio

Allison, P. D.
1982	Discrete-time methods for the analysis of event histories, in 
Sociological Methodology, a cura di S. Leinhard, San Francisco, 
Jossey-Bass,  pp. 61-98.



-----------------------------------------------------------
Teresio Poggio
Dept. of Sociology and Social Research
University of Trento
Via Verdi, 26 - 38100 Trento - Italy
E-mail: teresio.poggio@soc.unitn.it
        teresio.poggio@poste.it
-----------------------------------------------------------










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