data simple;
  infile 'data/SnP-static-pools.txt';
  do year = 1981 to 2002;
    input yr / ; drop yr;
    if yr ne year then abort;
    do initrtg = 'AAA', 'AA', 'A', 'BBB', 'BB', 'B', 'CCC';
      input ir $ issuers @; drop ir issuers;
      if ir ne initrtg then abort;
      do finalrtg = 'AAA', 'AA', 'A', 'BBB', 'BB', 'B', 'CCC', 'D', 'NR';
        input pct @; drop pct;
        count = round(pct * issuers / 100);
        if finalrtg ne 'NR' then output;
      end;
    end;
  end;

proc print data = simple;
run;