| Value | Category | Cases | |
|---|---|---|---|
| 1982 | 2 | 
                                    
                                    0.1%
                                 | |
| 1987 | 13 | 
                                    
                                    0.3%
                                 | |
| 1988 | 5 | 
                                    
                                    0.1%
                                 | |
| 1989 | 13 | 
                                    
                                    0.3%
                                 | |
| 1990 | 31 | 
                                    
                                    0.8%
                                 | |
| 1991 | 11 | 
                                    
                                    0.3%
                                 | |
| 1992 | 63 | 
                                    
                                    1.7%
                                 | |
| 1993 | 104 | 
                                    
                                    2.8%
                                 | |
| 1994 | 119 | 
                                    
                                    3.1%
                                 | |
| 1995 | 129 | 
                                    
                                    3.4%
                                 | |
| 1996 | 121 | 
                                    
                                    3.2%
                                 | |
| 1997 | 251 | 
                                    
                                    6.6%
                                 | |
| 1998 | 313 | 
                                    
                                    8.3%
                                 | |
| 1999 | 1253 | 
                                    
                                    33.2%
                                 | |
| 2000 | 776 | 
                                    
                                    20.5%
                                 | |
| 9998 | don't know | 574 | 
                                    
                                    15.2%
                                 | 
| Sysmiss | 11168 |