st: model fit comparison for xtgee

[tlum@umn.edu]

I am comparing two xtgee models to see how much explanatory power has 
increased
by adding a block of variables. I did a hausman test and the null 
hypothesis
was rejected. I do want to know how much more variance was explained by the 
new variables. Can the xtgee generate something like r-square type model 
fit index. Or is there anyway I can come up with some formal indicators for 
improvement in model fit under the new model.

Thanks in advance. 

Terry 
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