              
                                                                                                                             16                5            5                   1998             10%    5 16                                  
                        1942   7                                                             1966                               1991   1996   5    15 19          32.4 %               65.8%  55.9%                            
                                                                                                                                                                                                                                      1/3                                                                                                                                                               
                                                                                                                                                                                                         
              
                      72.5%                   79.2%     72.5%      56 %      47%                                                                               
                                                                                                                                   
     1988   8                             1996  1998                                2008   12                                                                                                                                                                                                                                                                                                                                2004     24               56     5          6          8                                          2003                                          
                         
                                                                                                                                                                                                                                                                                                 
                                                                                                           
                  
                                                                                                                                                                                                                                                  
                                                                                                                                                                                                                                                                                                                                                        
            2012 6 12