Annual % of total
1960 93.75287612951179
1961 93.57544680872911
1962 93.67088811744705
1963 93.93110247042964
1964 94.11113865719096
1965 93.95495435238006
1966 93.43431899975701
1967 93.5098963821609
1968 93.54896715353127
1969 93.81762985408437
1970 93.61227862848168
1971 93.87001841706923
1972 93.3399710147222
1973 93.78255538270167
1974 93.4444027586626
1975 92.72491955411434
1976 92.99609428097628
1977 91.90301841129364
1978 91.78857577247676
1979 91.74826756951178
1980 91.03050454394989
1981 89.21201412370672
1982 88.49034299509326
1983 87.27272345167712
1984 85.53891722123461
1985 84.2539331970632
1986 83.75479212233819
1987 83.46446323910155
1988 82.50451942264515
1989 82.06105400737948
1990 86.71457386734792
1991 86.4030784273993
1992 85.50897922036373
1993 84.61249467018274
1994 84.10059851507185
1995 83.7905108510317
1996 83.36162729876055
1997 82.84719651662536
1998 82.84127008555234
1999 82.5001139825607
2000 82.34366636238974
2001 82.13178802752287
2002 82.09195171815763
2003 82.27396695092662
2004 81.96154279812625
2005 81.77460714079608
2006 81.71437698470777
2007 81.61764450813031
2008 81.35234459358956
2009 80.26148449726824
2010 80.14902806270184
2011 80.21061627910724
2012 79.76864035028554
2013 78.80862160872547
2014 78.37981505963852
2015 71.5704915402549