| Value | Category | Cases | |
|---|---|---|---|
| -8 | Don’t Know | 7 |
3.5%
|
| 1937 | 1 |
0.5%
|
|
| 1953 | 1 |
0.5%
|
|
| 1954 | 1 |
0.5%
|
|
| 1955 | 1 |
0.5%
|
|
| 1957 | 1 |
0.5%
|
|
| 1960 | 4 |
2%
|
|
| 1962 | 1 |
0.5%
|
|
| 1963 | 2 |
1%
|
|
| 1965 | 3 |
1.5%
|
|
| 1968 | 4 |
2%
|
|
| 1969 | 2 |
1%
|
|
| 1970 | 2 |
1%
|
|
| 1972 | 2 |
1%
|
|
| 1974 | 2 |
1%
|
|
| 1975 | 11 |
5.5%
|
|
| 1976 | 2 |
1%
|
|
| 1977 | 2 |
1%
|
|
| 1978 | 2 |
1%
|
|
| 1979 | 3 |
1.5%
|
|
| 1980 | 3 |
1.5%
|
|
| 1981 | 1 |
0.5%
|
|
| 1982 | 7 |
3.5%
|
|
| 1983 | 3 |
1.5%
|
|
| 1984 | 2 |
1%
|
|
| 1985 | 2 |
1%
|
|
| 1986 | 1 |
0.5%
|
|
| 1987 | 1 |
0.5%
|
|
| 1988 | 1 |
0.5%
|
|
| 1989 | 2 |
1%
|
|
| 1990 | 4 |
2%
|
|
| 1991 | 8 |
4%
|
|
| 1992 | 5 |
2.5%
|
|
| 1993 | 5 |
2.5%
|
|
| 1994 | 4 |
2%
|
|
| 1995 | 3 |
1.5%
|
|
| 1996 | 5 |
2.5%
|
|
| 1997 | 10 |
5%
|
|
| 1998 | 2 |
1%
|
|
| 1999 | 4 |
2%
|
|
| 2000 | 4 |
2%
|
|
| 2001 | 4 |
2%
|
|
| 2002 | 7 |
3.5%
|
|
| 2003 | 5 |
2.5%
|
|
| 2004 | 4 |
2%
|
|
| 2005 | 7 |
3.5%
|
|
| 2006 | 10 |
5%
|
|
| 2007 | 4 |
2%
|
|
| 2008 | 4 |
2%
|
|
| 2009 | 5 |
2.5%
|
|
| 2010 | 4 |
2%
|
|
| 2011 | 3 |
1.5%
|
|
| 2012 | 2 |
1%
|
|
| 2013 | 4 |
2%
|
|
| 2014 | 2 |
1%
|
|
| 2015 | 2 |
1%
|
|
| 2016 | 2 |
1%
|