| Value | Category | Cases | |
|---|---|---|---|
| 1990 | 399 | 
                                                                 
                                    
                                    82.1%
                                 
                                                             | 
                                                        
                    |
| 1991 | 16 | 
                                                                 
                                    
                                    3.3%
                                 
                                                             | 
                                                        
                    |
| 1992 | 13 | 
                                                                 
                                    
                                    2.7%
                                 
                                                             | 
                                                        
                    |
| 1993 | 20 | 
                                                                 
                                    
                                    4.1%
                                 
                                                             | 
                                                        
                    |
| 1994 | 15 | 
                                                                 
                                    
                                    3.1%
                                 
                                                             | 
                                                        
                    |
| 1995 | 14 | 
                                                                 
                                    
                                    2.9%
                                 
                                                             | 
                                                        
                    |
| 1996 | 4 | 
                                                                 
                                    
                                    0.8%
                                 
                                                             | 
                                                        
                    |
| 1997 | 5 | 
                                                                 
                                    
                                    1%
                                 
                                                             | 
                                                        
                    |
| Sysmiss | 435 |