Annual % of total
1960 91.14805621570406
1961 91.19144207501691
1962 91.78950899432684
1963 91.99572478646634
1964 92.67797122262348
1965 92.68585722392939
1966 93.11888916183618
1967 94.4052172459684
1968 94.72148855185715
1969 95.23342118969605
1970 95.52565262261086
1971 72.97008621907129
1972 73.74900645497671
1973 75.0956033468099
1974 74.62725187604396
1975 74.83156040742372
1976 75.39160905496524
1977 76.70228660431268
1978 76.9825509056768
1979 76.98601348074396
1980 76.20906123168866
1981 75.43414202837825
1982 75.06548108740805
1983 75.06475883372437
1984 75.47822564321682
1985 74.91536252008729
1986 75.29719595522106
1987 75.33150733433109
1988 76.40001355620392
1989 76.55935919156941
1990 77.0420466511168
1991 76.68828066323618
1992 77.26621616408978
1993 77.77506350451881
1994 78.3424010092597
1995 78.80392075799325
1996 79.17434459591334
1997 79.21677269306417
1998 78.65015110662097
1999 79.13821678308949
2000 79.19559548414736
2001 79.84971034638978
2002 80.57916429371834
2003 82.0243363920613
2004 82.81005273398134
2005 83.25583853364672
2006 83.90158360304147
2007 84.74013955891188
2008 84.5400858662495
2009 84.54991928702403
2010 85.16201539665532
2011 86.59731780993042
2012 86.74263228281538
2013 86.7237300526565
2014 86.3961530004804
2015 87.88536414825094