| Value | Category | Cases | |
|---|---|---|---|
| 1997 | 1 | 
                                    
                                    3.2%
                                 | |
| 1998 | 1 | 
                                    
                                    3.2%
                                 | |
| 1999 | 5 | 
                                    
                                    16.1%
                                 | |
| 2000 | 9 | 
                                    
                                    29%
                                 | |
| 2001 | 13 | 
                                    
                                    41.9%
                                 | |
| 2002 | 2 | 
                                    
                                    6.5%
                                 | |
| Sysmiss | 11283 |