| Value | Category | Cases | |
|---|---|---|---|
| 1997 | 1 | 
                                    
                                    1.5%
                                 | |
| 1998 | 3 | 
                                    
                                    4.6%
                                 | |
| 1999 | 7 | 
                                    
                                    10.8%
                                 | |
| 2000 | 12 | 
                                    
                                    18.5%
                                 | |
| 2001 | 27 | 
                                    
                                    41.5%
                                 | |
| 2002 | 15 | 
                                    
                                    23.1%
                                 | |
| Sysmiss | 7984 |