| Value | Category | Cases | |
|---|---|---|---|
| 1997 | 1 | 
                                    
                                    2.2%
                                 | |
| 1999 | 3 | 
                                    
                                    6.5%
                                 | |
| 2000 | 1 | 
                                    
                                    2.2%
                                 | |
| 2002 | 3 | 
                                    
                                    6.5%
                                 | |
| 2003 | 8 | 
                                    
                                    17.4%
                                 | |
| 2004 | 8 | 
                                    
                                    17.4%
                                 | |
| 2005 | 12 | 
                                    
                                    26.1%
                                 | |
| 2006 | 9 | 
                                    
                                    19.6%
                                 | |
| 2007 | 1 | 
                                    
                                    2.2%
                                 | |
| Sysmiss | 876 |