| Value | Category | Cases | |
|---|---|---|---|
| 1969 | 1 | 
                                    
                                    0%
                                 | |
| 1970 | 3 | 
                                    
                                    0.1%
                                 | |
| 1971 | 6 | 
                                    
                                    0.3%
                                 | |
| 1972 | 5 | 
                                    
                                    0.2%
                                 | |
| 1973 | 8 | 
                                    
                                    0.4%
                                 | |
| 1974 | 8 | 
                                    
                                    0.4%
                                 | |
| 1975 | 9 | 
                                    
                                    0.4%
                                 | |
| 1976 | 5 | 
                                    
                                    0.2%
                                 | |
| 1977 | 9 | 
                                    
                                    0.4%
                                 | |
| 1978 | 20 | 
                                    
                                    1%
                                 | |
| 1979 | 30 | 
                                    
                                    1.4%
                                 | |
| 1980 | 18 | 
                                    
                                    0.9%
                                 | |
| 1981 | 16 | 
                                    
                                    0.8%
                                 | |
| 1982 | 28 | 
                                    
                                    1.4%
                                 | |
| 1983 | 34 | 
                                    
                                    1.6%
                                 | |
| 1984 | 31 | 
                                    
                                    1.5%
                                 | |
| 1985 | 44 | 
                                    
                                    2.1%
                                 | |
| 1986 | 58 | 
                                    
                                    2.8%
                                 | |
| 1987 | 48 | 
                                    
                                    2.3%
                                 | |
| 1988 | 59 | 
                                    
                                    2.9%
                                 | |
| 1989 | 54 | 
                                    
                                    2.6%
                                 | |
| 1990 | 91 | 
                                    
                                    4.4%
                                 | |
| 1991 | 72 | 
                                    
                                    3.5%
                                 | |
| 1992 | 104 | 
                                    
                                    5%
                                 | |
| 1993 | 125 | 
                                    
                                    6%
                                 | |
| 1994 | 123 | 
                                    
                                    5.9%
                                 | |
| 1995 | 135 | 
                                    
                                    6.5%
                                 | |
| 1996 | 133 | 
                                    
                                    6.4%
                                 | |
| 1997 | 178 | 
                                    
                                    8.6%
                                 | |
| 1998 | 202 | 
                                    
                                    9.8%
                                 | |
| 1999 | 291 | 
                                    
                                    14.1%
                                 | |
| 2000 | 121 | 
                                    
                                    5.8%
                                 | |
| 9997 | inconsistent | 0 | 
                                    
                                    0%
                                 | 
| 9998 | dk | 0 | 
                                    
                                    0%
                                 | 
| Sysmiss | 13282 |