st: areg/xtreg

[Terra Curtis <terra.curtis@cambridgefinance.com>]

I am using Stata 8.2.  I have a question regarding what is written in 
the Stata manual for -areg-.  The manual reports that "-areg- identifies 
the model by choosing the intercept that makes the prediction calculated 
at the means of the independent variables equal to the mean of the 
dependent variable: y(hat)=x(hat)*beta"

I have used this fact to try to calculate the "percent of mean 
explained" by each independent variable in my regression.  For 
concreteness, I have regressed like this:

areg depvar indvar1 indvar2 indvar3, absorb(timevar)

For the percent of mean explained calculation, I have taken each 
coefficient multiplied by the mean of that independent variable and 
divided by the mean of the dependent variable.  After I have done this 
for all three independent variables, in theory the three percentages 
should add up to 1.  However, this is not the case.  Can anyone see why not?

Thank you,
Terra Curtis
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/