Annual % of total
1960 93.09282886053674
1961 92.05548549810845
1962 93.30262225372077
1963 94.12515964240103
1964 94.17309340188518
1965 93.44348282192499
1966 94.17784853309075
1967 93.64440868865647
1968 93.85299934080422
1969 93.23067051652228
1970 94.73216928085232
1971 94.08480659311445
1972 94.23103591734849
1973 93.38525924203674
1974 93.91064136440068
1975 92.9988726042841
1976 93.12108559498957
1977 92.33762346602813
1978 91.87866927592955
1979 91.95192307692307
1980 90.31714568880079
1981 90.3734264254734
1982 89.19740150880135
1983 87.61648374404638
1984 82.61949834358731
1985 81.54007059746372
1986 83.90458254865035
1987 84.34870414002019
1988 84.13840023325882
1989 86.87464867903317
1990 85.65910871694417
1991 90.06682606541129
1992 94.20324262520009
1993 87.05454909397388
1994 88.990613592233
1995 82.10401132686084
1996 74.1441428359757
1997 75.7058064516129
1998 74.64177765914854
1999 70.41369045975424
2000 69.69253996447603
2001 69.89659132133389
2002 64.54201535508638
2003 60.264940484151396
2004 60.97732835429769
2005 53.788927016645324
2006 54.62954808642847
2007 49.1818669527897
2008 51.16499674182198
2009 49.90563725490196
2010 49.81626301304296
2011 46.18588019415177
2012 47.08884397002044
2013 42.35797443762782
2014 42.1769974140408
2015 45.74797835840591
2016 44.980340217739354