Year % of total 1960 0 1961 0 1962 0 1963 0 1964 0 1965 0 1966 0 1967 0 1968 0 1969 1.4598540145985401 1970 14.102564102564102 1971 20.32085561497326 1972 24.30939226519337 1973 2.402402402402402 1974 2.0316027088036117 1975 3.0000000000000004 1976 1.1869436201780414 1977 0 1978 1.1363636363636362 1979 1.0526315789473684 1980 0.9009009009009009 1981 0 1982 0.2724795640326975 1983 0.3205128205128205 1984 0.3215434083601286 1985 0.5730659025787965 1986 0.3436426116838488 1987 0.27700831024930744 1988 0.24449877750611243 1989 0.24330900243309003 1990 0.4365476190476191 1991 0.11905844155844156 1992 3.411162790697674 1993 6.745317725752509 1994 7.254856115107914 1995 6.8834470989761085 1996 7.203035714285715 1997 7.575538922155689 1998 7.833529411764706 1999 9.322881355932203 2000 8.334090909090909 2001 0 2002 0 2003 1.1225510204081632 2004 1.2821678321678323 2005 0.9129460580912862 2006 0.888969696969697 2007 0.7862962962962964 2008 0.8811645101663585 2009 1.9548345588235296 2010 3.9026305220883533 2011 5.809855967078189 2012 8.569199999999999 2013 14.484649999999998 2014 12.852475490196078 2015 15.243633720930234 2016 14.558537313432836