DSDR KB:

Here’s an example of how you can sum in SAS.

The example has you multiplying size of census tract x pov for each census tract (in the neighborhood).

Sort by neighborhood. Sum these products across all census tracts in the neighborhood. End up with a single sum for a zip code

data a;
infile . . . ;
input . . . ;
wpov = total*pov;
proc sort; by neigh;
proc means noprint data=a;
by neigh;
var wpov;
output out=sum sum(wpov)=wpovx;
data b;
set sum;
proc print;
neigh wpovx;