Produce the block map. The LEVELS= option specifies the number of response levels for the graph. The SHAPE= option draws the blocks as prisms. The RELZERO option specifies that the block values are relative to zero. The CEMPTY= option specifies the outline color for map areas that have missing data.

proc gmap data=sashelp.demographics(where=(cont=92))
          map=maps.samerica all;
   id id;
   block gni / levels=3 shape=prism
               relzero cempty=gray;
run;
quit;