| Value | Category | Cases | |
|---|---|---|---|
| 1997 | 2 | 
                                    
                                    8%
                                 | |
| 1998 | 2 | 
                                    
                                    8%
                                 | |
| 1999 | 3 | 
                                    
                                    12%
                                 | |
| 2000 | 9 | 
                                    
                                    36%
                                 | |
| 2001 | 7 | 
                                    
                                    28%
                                 | |
| 2002 | 2 | 
                                    
                                    8%
                                 | |
| Sysmiss | 8024 |