| Value | Category | Cases | |
|---|---|---|---|
| -8 | Don’t Know | 69 | 
                                    
                                    3.5%
                                 | 
| 1937 | 10 | 
                                    
                                    0.5%
                                 | |
| 1953 | 10 | 
                                    
                                    0.5%
                                 | |
| 1954 | 10 | 
                                    
                                    0.5%
                                 | |
| 1955 | 10 | 
                                    
                                    0.5%
                                 | |
| 1957 | 10 | 
                                    
                                    0.5%
                                 | |
| 1960 | 40 | 
                                    
                                    2%
                                 | |
| 1962 | 10 | 
                                    
                                    0.5%
                                 | |
| 1963 | 20 | 
                                    
                                    1%
                                 | |
| 1965 | 30 | 
                                    
                                    1.5%
                                 | |
| 1968 | 40 | 
                                    
                                    2%
                                 | |
| 1969 | 20 | 
                                    
                                    1%
                                 | |
| 1970 | 20 | 
                                    
                                    1%
                                 | |
| 1972 | 21 | 
                                    
                                    1.1%
                                 | |
| 1974 | 22 | 
                                    
                                    1.1%
                                 | |
| 1975 | 105 | 
                                    
                                    5.3%
                                 | |
| 1976 | 21 | 
                                    
                                    1.1%
                                 | |
| 1977 | 20 | 
                                    
                                    1%
                                 | |
| 1978 | 14 | 
                                    
                                    0.7%
                                 | |
| 1979 | 24 | 
                                    
                                    1.2%
                                 | |
| 1980 | 41 | 
                                    
                                    2.1%
                                 | |
| 1981 | 10 | 
                                    
                                    0.5%
                                 | |
| 1982 | 67 | 
                                    
                                    3.4%
                                 | |
| 1983 | 30 | 
                                    
                                    1.5%
                                 | |
| 1984 | 20 | 
                                    
                                    1%
                                 | |
| 1985 | 20 | 
                                    
                                    1%
                                 | |
| 1986 | 10 | 
                                    
                                    0.5%
                                 | |
| 1987 | 10 | 
                                    
                                    0.5%
                                 | |
| 1988 | 10 | 
                                    
                                    0.5%
                                 | |
| 1989 | 20 | 
                                    
                                    1%
                                 | |
| 1990 | 40 | 
                                    
                                    2%
                                 | |
| 1991 | 76 | 
                                    
                                    3.9%
                                 | |
| 1992 | 51 | 
                                    
                                    2.6%
                                 | |
| 1993 | 52 | 
                                    
                                    2.6%
                                 | |
| 1994 | 40 | 
                                    
                                    2%
                                 | |
| 1995 | 30 | 
                                    
                                    1.5%
                                 | |
| 1996 | 47 | 
                                    
                                    2.4%
                                 | |
| 1997 | 102 | 
                                    
                                    5.2%
                                 | |
| 1998 | 20 | 
                                    
                                    1%
                                 | |
| 1999 | 47 | 
                                    
                                    2.4%
                                 | |
| 2000 | 37 | 
                                    
                                    1.9%
                                 | |
| 2001 | 35 | 
                                    
                                    1.8%
                                 | |
| 2002 | 64 | 
                                    
                                    3.3%
                                 | |
| 2003 | 50 | 
                                    
                                    2.5%
                                 | |
| 2004 | 41 | 
                                    
                                    2.1%
                                 | |
| 2005 | 68 | 
                                    
                                    3.5%
                                 | |
| 2006 | 95 | 
                                    
                                    4.8%
                                 | |
| 2007 | 41 | 
                                    
                                    2.1%
                                 | |
| 2008 | 41 | 
                                    
                                    2.1%
                                 | |
| 2009 | 51 | 
                                    
                                    2.6%
                                 | |
| 2010 | 39 | 
                                    
                                    2%
                                 | |
| 2011 | 31 | 
                                    
                                    1.6%
                                 | |
| 2012 | 16 | 
                                    
                                    0.8%
                                 | |
| 2013 | 35 | 
                                    
                                    1.8%
                                 | |
| 2014 | 20 | 
                                    
                                    1%
                                 | |
| 2015 | 21 | 
                                    
                                    1.1%
                                 | |
| 2016 | 13 | 
                                    
                                    0.7%
                                 |