Annual % of total
1960 85.61042089546577
1961 87.61714451333104
1962 89.31098023879356
1963 89.16118114620792
1964 90.11980938700768
1965 90.05268689030589
1966 90.5498640135678
1967 91.62898255205472
1968 92.43561267997363
1969 93.30522622813245
1970 93.31802377874833
1971 93.46442774222035
1972 93.73671180088743
1973 94.54555308918347
1974 93.68373786509898
1975 93.16201775845066
1976 93.92315188490858
1977 93.0277292510405
1978 93.49310257347769
1979 93.84406981323497
1980 93.73038865548506
1981 93.35108724122307
1982 92.58894558045996
1983 92.52218785314437
1984 91.61572111307194
1985 91.81477521491752
1986 91.45783236568886
1987 93.38343377293097
1988 92.9048437377345
1989 93.29463061557998
1990 93.43818883146562
1991 92.89537207529075
1992 92.58124189283532
1993 92.2702900571247
1994 92.08793744899538
1995 93.02465206686588
1996 92.61465540907994
1997 92.44346417646835
1998 92.28589095434627
1999 91.8413718480898
2000 91.73009539319074
2001 91.40342478836986
2002 91.0358673382802
2003 90.21611169609193
2004 90.40624236209705
2005 89.80144618009906
2006 89.19087872196356
2007 88.18304312073485
2008 86.84215310440152
2009 84.85132566692076
2010 84.6287740206212
2011 84.4647972084689
2012 82.20135574290676
2013 79.96433458668163
2014 78.5864226219386
2015 79.94845473549468