Annual % of total
1960 98.2469031231268
1961 98.30405988617062
1962 98.39621714892378
1963 98.42085721457043
1964 98.51842370724432
1965 98.48322188231803
1966 98.38041687988124
1967 98.31815928977687
1968 98.3266400666609
1969 98.3094082750672
1970 98.51603953277217
1971 98.40003407221528
1972 98.26794321575471
1973 98.66049858790944
1974 98.69160455994891
1975 98.53120515681304
1976 98.66290759905787
1977 98.6172507561971
1978 98.86159799517642
1979 99.0083998374476
1980 98.89705035969236
1981 98.56129193618156
1982 98.87214426086646
1983 98.89132840826318
1984 98.77884300269045
1985 98.5598041581933
1986 97.84634048601613
1987 97.98890245619786
1988 97.79065687748037
1989 97.89936156850955
1990 97.80680713313512
1991 98.05065912629333
1992 98.04603324369624
1993 95.58676875122154
1994 95.33847707321208
1995 95.45551646072143
1996 95.89704630302501
1997 95.89721099215625
1998 96.10865233975404
1999 96.31842863673408
2000 96.21984176705291
2001 95.98089994469619
2002 95.87003043771405
2003 96.24775866466713
2004 95.9787564750952
2005 95.99393988720713
2006 95.82033864257387
2007 95.21206560207278
2008 94.11388883610816
2009 93.15405778543386
2010 92.45120756925895
2011 92.11514123463645
2012 90.97851870869306
2013 91.14640642360806
2014 90.08796429578791
2015 90.29137543565525