After the Department of Revenue has examined and compared the summaries and obtained the other necessary information, the department shall combine the result in a table. When approved by the Director of the Department of Revenue, a table shall be signed by the director and retained on file in the department. [Amended by 1969 c.520 §37; 1981 c.804 §25; 1985 c.761 §14; 1991 c.459 §203b; 1993 c.98 §14; 1997 c.541 §240]