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Re: st: age when having first child


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: age when having first child
Date   Fri, 9 Jun 2006 13:53:45 +0100 (BST)

--- Dirk Nachbar wrote:
> I have survey data for one year from which I want to estimate 
> an equation for the age a person had his first child. I 
> derive the independent variable from the adult's and oldest 
> child's age. When I regress that equation I have significantly 
> positive cohort effects for old cohorts which I find quite 
> puzzling for my UK sample. My expectation was that the age 
> someone had a child would increase over time. Do you have any 
> views on what might have gone wrong.

Dirk Nachbar:
This is not a lot of information to go on, but three thoughts 
jump to mind: The oldest cohort in a sample is usually quite 
small, in which case this could be sampling variation. If the 
oldest cohort is very old (say >80 years) than selection may 
play a roll: you can only get answers from people who are still 
alive and are sufficiently lucid to understand and answer a 
questionnaire. Better educated people stay alive and healthy 
longer and they get children at a later age. Another cause 
could be if the oldest cohort includes people getting children 
just after World War II. In the Netherlands people postponed 
getting children during WWII, hence this cohort would get children 
at an older age. I would imagine that something similar occurred 
in the UK, even though you weren't occupied.

HTH,

Maarten

 

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology 
Vrije Universiteit Amsterdam 
Boelelaan 1081 
1081 HV Amsterdam 
The Netherlands
 
visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z214 
 
+31 20 5986715
 
http://home.fsw.vu.nl/m.buis/
-----------------------------------------

 



-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z214

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------

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