| Value | Category | Cases | |
|---|---|---|---|
| 1998 | 2 | 
                                    
                                    6.3%
                                 | |
| 1999 | 5 | 
                                    
                                    15.6%
                                 | |
| 2000 | 3 | 
                                    
                                    9.4%
                                 | |
| 2001 | 7 | 
                                    
                                    21.9%
                                 | |
| 2002 | 15 | 
                                    
                                    46.9%
                                 | |
| Sysmiss | 8017 |