Annual % of total
1960 95.93482569772576
1961 94.71736964463634
1962 93.6196257713158
1963 93.07570871960232
1964 91.98405371380612
1965 91.04461513570982
1966 89.93168076539988
1967 88.61558775731311
1968 88.0855190103067
1969 86.89443124499726
1970 86.36549410232769
1971 84.07512758303353
1972 82.80054951327138
1973 80.98620344989475
1974 78.61591335911578
1975 79.20521110079703
1976 76.1692800539538
1977 76.27398027006228
1978 76.48650614314698
1979 76.82925632647454
1980 76.58051471231447
1981 77.56955041078447
1982 79.09319373185656
1983 79.35825324513917
1984 80.19073404319803
1985 80.6389897889924
1986 80.17255894493746
1987 80.17882716858644
1988 79.94286324475485
1989 79.7914176746877
1990 91.02507159421357
1991 89.11508137903475
1992 87.52240887775105
1993 84.37846720105314
1994 86.20203003003002
1995 83.37005397310098
1996 86.87385359296286
1997 83.47665622552857
1998 75.70179161046
1999 75.58873313857488
2000 71.72026916141611
2001 68.92587506911462
2002 73.02532779459763
2003 75.27241834908118
2004 74.94252216492934
2005 76.0941948267092
2006 76.32865822127486
2007 71.24770038393238
2008 79.69641330588838
2009 72.76236661564126
2010 77.61191904440905
2011 78.84861200118557
2012 78.3672912481735
2013 75.47377043439056
2014 75.10046714785537
2015 73.98380452330163
2016 70.83180489509706