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Re: st: Multivariate Tobit


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Multivariate Tobit
Date   Fri, 30 Jun 2006 21:15:21 +0100 (BST)

--- Diana Fletschner <fletschn@u.washington.edu> wrote:
> I am trying to analyze how spouses who save structure their savings 
> portfolio. That is, what percentage of their savings is in joint
> accounts, or under his name, or under her name. A basic approach
would
> be to use three Tobit models given that the three dependent variables

> are bounded between 0 and 100. However, I want to estimate them 
> jointly as a Multivariate Tobit given that the errors are likely to
be
> correlated due to unobserved household characteristics. And, I would
> like to impose restrictions on the coefficients taking advantage of 
> the fact that we know the sum of the three  dependent variables has
to
> equal 100.

If I understand you correctly you want to model three dependent
variables: proportion savings in joint account, in her account, and in
his account, and these proportions should add up to one. -dirifit- will
jointly estimate a model with multiple proportions as dependent
variables which should add up to one. One disadvantage is that the
proportions must be between zero and one and can not include zero and
one, so you might need to add and subtract some arbitrary small number
when couples have no money in one of the categories. 

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/
-----------------------------------------


	
	
		
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