| Value | Category | Cases | |
|---|---|---|---|
| 1964 | 1 | 
                                    
                                    0%
                                 | |
| 1972 | 1 | 
                                    
                                    0%
                                 | |
| 1973 | 1 | 
                                    
                                    0%
                                 | |
| 1974 | 1 | 
                                    
                                    0%
                                 | |
| 1975 | 2 | 
                                    
                                    0.1%
                                 | |
| 1977 | 1 | 
                                    
                                    0%
                                 | |
| 1980 | 1 | 
                                    
                                    0%
                                 | |
| 1981 | 4 | 
                                    
                                    0.2%
                                 | |
| 1982 | 3 | 
                                    
                                    0.1%
                                 | |
| 1983 | 7 | 
                                    
                                    0.3%
                                 | |
| 1984 | 7 | 
                                    
                                    0.3%
                                 | |
| 1985 | 11 | 
                                    
                                    0.5%
                                 | |
| 1986 | 8 | 
                                    
                                    0.4%
                                 | |
| 1987 | 17 | 
                                    
                                    0.8%
                                 | |
| 1988 | 29 | 
                                    
                                    1.4%
                                 | |
| 1989 | 19 | 
                                    
                                    0.9%
                                 | |
| 1990 | 40 | 
                                    
                                    2%
                                 | |
| 1991 | 37 | 
                                    
                                    1.8%
                                 | |
| 1992 | 48 | 
                                    
                                    2.4%
                                 | |
| 1993 | 95 | 
                                    
                                    4.7%
                                 | |
| 1994 | 106 | 
                                    
                                    5.2%
                                 | |
| 1995 | 133 | 
                                    
                                    6.5%
                                 | |
| 1996 | 153 | 
                                    
                                    7.5%
                                 | |
| 1997 | 185 | 
                                    
                                    9.1%
                                 | |
| 1998 | 271 | 
                                    
                                    13.3%
                                 | |
| 1999 | 537 | 
                                    
                                    26.4%
                                 | |
| 2000 | 316 | 
                                    
                                    15.5%
                                 | |
| 9997 | inconsistent | 0 | 
                                    
                                    0%
                                 | 
| 9998 | dk | 1 | 
                                    
                                    0%
                                 | 
| Sysmiss | 13316 |