Annual % of total
1960 44.199071887423855
1961 44.15911346707507
1962 49.04966574217519
1963 51.626279505991334
1964 53.97489236859649
1965 56.08172970749894
1966 59.44922183786405
1967 60.624610711811265
1968 62.18319546684407
1969 64.16108790981964
1970 65.65402953079007
1971 68.9916544018548
1972 70.281428060387
1973 72.39128652262511
1974 72.57193154195656
1975 72.37632892449287
1976 73.1048969013744
1977 74.85099186451689
1978 73.69749532972655
1979 70.98886767012519
1980 71.91816933490009
1981 71.59576614035046
1982 72.17232929224983
1983 73.87615827891497
1984 74.38064344323263
1985 76.59234288265311
1986 77.982477519525
1987 78.86663214238764
1988 77.03619447551004
1989 79.78316107678481
1990 81.76598213448534
1991 81.41887116379289
1992 81.37420132978683
1993 81.38847422503758
1994 81.61678500615336
1995 82.59288875127184
1996 83.23558002394722
1997 83.78303175933559
1998 83.63248921254406
1999 84.53000918999322
2000 86.24798514041633
2001 86.07294034621975
2002 86.0700877177666
2003 87.04065847056532
2004 86.70136113677515
2005 88.05963777594144
2006 89.00397079154581
2007 90.4967522808164
2008 90.56269753228712
2009 89.89750931308214
2010 89.12433056785412
2011 89.9693974614175
2012 89.41051233775535
2013 88.15732151089873
2014 89.54395090120968
2015 86.84318766070803