Annual % of total
1960 80.6161238329836
1961 80.48705042040437
1962 79.6186483999591
1963 79.27128203907756
1964 77.77615500705906
1965 77.61428161110007
1966 75.33784505027647
1967 76.48711943793911
1968 73.11644841153327
1969 71.55024898579147
1970 70.03532772098617
1971 68.22286742309542
1972 68.23155130622138
1973 67.94978669151178
1974 69.44281988461233
1975 70.76305688030709
1976 70.83617154375477
1977 70.36584404320745
1978 68.25818318415565
1979 67.29740745772762
1980 69.51525696869197
1981 68.6565225860912
1982 67.42739677179145
1983 67.92396188410288
1984 65.97821260192175
1985 65.66713935799923
1986 66.03890015306817
1987 66.0918849936191
1988 66.50332249006034
1989 64.88470331925242
1990 72.07915908121177
1991 71.58662166167221
1992 72.2077717132612
1993 73.42992290833294
1994 73.27656908205539
1995 70.41025947915261
1996 71.84906555772994
1997 71.06118189122073
1998 69.03476917947681
1999 68.58189217887599
2000 67.40287437378348
2001 67.5012785675347
2002 67.05151813109474
2003 68.15149947336818
2004 68.16695950109916
2005 70.14530666057271
2006 70.47132938027589
2007 69.7498475413517
2008 70.75717398938113
2009 69.3911244923591
2010 65.66539581219112
2011 68.76645462289869
2012 71.44345143222412
2013 67.42655442061003
2014 69.62558522511898
2015 69.20933397512813
2016 69.46453015646183