Two versions of an easy-to-use, public-domain computer program that
implement all the statistical and graphical methods proposed herein
are available from my homepage on the World Wide Web at
http://GKing.Harvard.Edu.
One version, EI: A Program for Ecological Inference, works
under the Gauss software package and is also distributed with Gauss,
as part of its Constrained Maximum Likelihood module.
The other version, 
: A(n easy)
Program for Ecological Inference, by Ken Benoit and me, is a
stand-alone, menu-based system that is less flexible but does not
require any other software. The methods introduced here are also
being incorporated in several general-purpose statistical packages;
when these are complete, I will list this information at my homepage.
In order to meet the replication standard (King, 1995), I have deposited all data used in this manuscript, all computer software written for it, and all additional information necessary to replicate the empirical results herein with Inter-University Consortium for Political and Social Research (ICPSR) in their Publication-Related Archive.