Year % of total 1960 91.25636672325977 1961 92.25978647686833 1962 92.6873857404022 1963 93.29371816638371 1964 93.72485921158487 1965 94.22310756972111 1966 93.82632293080054 1967 93.54354354354354 1968 92.94294294294293 1969 94.49541284403671 1970 94.6360153256705 1971 94.44444444444444 1972 94.74954737477368 1973 94.22222222222224 1974 93.87096774193547 1975 93.36609336609337 1976 93.09701492537313 1977 92.7968851395198 1978 93.93358876117497 1979 94.3341121495327 1980 92.90201005025128 1981 92.97407912687585 1982 93.0775018811136 1983 94.6205571565802 1984 95.11158342189161 1985 95.21690767519468 1986 94.69434832756632 1987 94.23274974253346 1988 95.42334096109842 1989 94.29000751314801 1990 97.24693506493507 1991 98.51391304347827 1992 103.09113207547169 1993 93.92093541202672 1994 86.99463700234192 1995 91.47953091684435 1996 93.59260550458714 1997 92.79620503597123 1998 90.7233564013841 1999 92.81079646017699 2000 89.66016483516484 2001 91.26755555555555 2002 90.0155408388521 2003 88.12233853006683 2004 93.48835164835164 2005 97.53813308687616 2006 96.68598736176935 2007 93.83758974358975 2008 100.4048258064516 2009 96.62329856584093 2010 92.6676592356688 2011 93.62655716162944 2012 95.54859154929576 2013 95.86016304347827 2014 95.90615384615384 2015 94.59635811836115 2016 96.08326186830016