Year % of total 1970 0.9681504689606034 1971 1.047032720417058 1972 1.063300850140397 1973 1.2050834192267883 1974 1.1061268875073245 1975 1.217538975503784 1976 1.1416670764121635 1977 1.1489883187973866 1978 1.2840268706107145 1979 1.3159847822004518 1980 1.4705091643974668 1981 1.5193530199253646 1982 1.586083566201066 1983 1.577015809569868 1984 1.580279095928944 1985 1.5265953309616616 1986 1.644593010141092 1987 1.688040985314378 1988 1.926484145900892 1989 1.93338260263253 1990 1.9607843137254901 1991 1.9607843137254901 1992 1.9230769230769231 1993 1.8867924528301887 1994 1.8518518518518516 1995 1.8181818181818181 1996 1.7857142857142856 1997 1.7857142857142856 1998 1.7543859649122806 1999 1.7241379310344827 2000 1.7543859649122806 2001 1.7241379310344827 2002 1.7543859649122806 2003 1.7543859649122806 2004 1.7543859649122806 2005 1.7857142857142856 2006 1.639344262295082 2007 1.639344262295082 2008 1.6666666666666667