If you specify the keyword SUM, the procedure computes the estimate of the population total from the survey data. The estimate
of the total is the weighted sum over the sample:
For a categorical variable level, 
estimates its total frequency in the population.
![\[ \widehat{Y} = \sum _{h=1}^ H\sum _{i=1}^{n_ h} \sum _{j=1}^{m_{hi}} ~ w_{hij} ~ y_{hij} \]](images/statug_surveymeans0076.png){kind=small}