Annual % of total
1960 98.2469031231268
1961 98.30405988617062
1962 98.39621714892378
1963 98.42085721457043
1964 98.51842370724432
1965 97.81227335823385
1966 97.80813345516523
1967 97.73769234204674
1968 97.84306045753839
1969 97.69032809473684
1970 97.99588636411977
1971 97.75131941395898
1972 97.64559402099279
1973 97.75988318158447
1974 97.52833947666007
1975 97.5478641117396
1976 97.46301961334476
1977 96.94853305660044
1978 97.247835293646
1979 97.48717968996998
1980 97.11355254471654
1981 96.55742895871141
1982 96.55668897906583
1983 96.2190621767041
1984 95.74603926013383
1985 95.01893745099947
1986 94.51202461249031
1987 94.02746948498982
1988 93.297837390067
1989 93.22472288932785
1990 89.25330505032075
1991 88.74399055760027
1992 88.52183424826393
1993 87.65971908158531
1994 86.96654716934603
1995 86.7928836368446
1996 86.35280843859
1997 85.71687480874043
1998 85.45168272177118
1999 85.16067308618699
2000 84.74255215818515
2001 84.67572611381378
2002 83.91131137246983
2003 83.95075141923327
2004 83.26790699260303
2005 83.18497664383997
2006 83.39174071863322
2007 83.06888312623224
2008 81.70598525004269
2009 79.88391258146733
2010 80.25491985092357
2011 80.09576321015646
2012 78.56672775805606
2013 77.7076786589043
2014 76.24536377075727
2015 79.36373837402914