Annual % of total
1960 44.199071887423855
1961 44.15911346707507
1962 49.0496657421752
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 56.18210452776711
1972 56.64035821403452
1973 57.82240217675722
1974 58.87666793032958
1975 59.25905648055704
1976 60.43458684612917
1977 61.63772528619459
1978 62.11382609607491
1979 63.45809749622697
1980 64.773308754404
1981 66.24525247468837
1982 67.28231449002314
1983 67.1787910311207
1984 67.37356051252719
1985 68.08271812182736
1986 68.40550484485658
1987 69.20655178324701
1988 69.73197145138603
1989 70.29494462958596
1990 71.19373646754657
1991 71.31681632060827
1992 71.82451964835627
1993 72.40467574018346
1994 73.03720213643994
1995 73.8844625521144
1996 74.19710848779731
1997 74.48672398056819
1998 74.79100823680497
1999 75.23841770002927
2000 75.21748327798758
2001 75.58610673382844
2002 75.85255509612962
2003 76.18531260022357
2004 76.82659726754952
2005 77.17107389240073
2006 77.6697272386685
2007 78.22968464277041
2008 78.82466983282586
2009 79.21596225323468
2010 79.28369723469687
2011 78.87501664601541
2012 79.3794253154833
2013 79.00253666660687
2014 79.50189014419063
2015 89.53660154092321