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st: RE: counterfactuals

From   "Millimet, Daniel" <>
To   <>
Subject   st: RE: counterfactuals
Date   Wed, 2 Oct 2002 21:00:05 -0500

you need to generate the predicted probabilities, replacing the black=1 variable to black=0 for black observations.  to do this, something along the following lines is needed:
1. run your logit
2. generate predicted indexes, not probabilities (i.e., predict yhat, xb)
3. replace yhat=yhat-_b[black] if black==1.
4. generate the probabilities as exp(yhat)/(1+exp(yhat)).
i think this is correct, but double check my formulas.  you should get the idea.

	-----Original Message----- 
	From: Traci A Schlesinger [mailto:tracias@Princeton.EDU] 
	Sent: Wed 10/2/2002 8:01 PM 
	Subject: st: counterfactuals

	dear statalisters:
	i tried to post this yesterday, but never saw it posted.  i apologize if
	this is a double post.
	I have county level data on criminal processing that includes whether
	the defendant is incarcerated pretrial and / or post-trial, as well as
	several legal variables regarding the type of offense the individual was
	arrested for and details of their prior record, and extra-legal
	variables such as race and age.
	i have used xtlogit, with county level fixed effects, to analyze this
	data, with specific interest in the effect of race and ethnicity on
	criminal processing.  i find that race and ethnicity affects both
	pretrial release decisions, and the decision to incarcerate given
	as a next step, i wanted to create counterfactuals that would look at
	what the predicted probability of release would be for the black and
	latino defendants if they were white (e.g. what would be the probability
	of being granted pretrial release if one had all of the legal
	characteristics of the black defendants but was white), or put
	differently, what would be the predicted probability of release for
	black defendants if the black coefficient equaled zero.
	i understand how to use the predict command to get predicted
	probabilities, but don't know how to get predicted values for this type
	of counterfactual situation.  i have read the manual and the FAQs, but i
	am still lost.
	any help would be greatly appreciated!!
	thanks in advance,
	traci a schlesinger
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