Annual % of total
1960 58.0896686159844
1961 57.22284434490482
1962 58.11688311688311
1963 54.98055638647921
1964 52.57903494176372
1965 53.11221193194056
1966 56.567046795123865
1967 58.85113572367185
1968 61.048135370461644
1969 59.11904419173744
1970 66.38846737481032
1971 65.9986816084377
1972 68.00232288037165
1973 68.49409448818898
1974 65.49559582869293
1975 60.588623714743896
1976 58.579729960690486
1977 59.4054771007256
1978 63.476205003050644
1979 61.810122962539324
1980 62.7379679144385
1981 59.10931174089068
1982 57.436185922227686
1983 52.43282498184458
1984 51.72568931165241
1985 49.261769333171976
1986 47.1937984496124
1987 47.44930383037726
1988 47.20888840947091
1989 48.77409787444389
1990 46.858266331658285
1991 49.17707201266156
1992 48.3445497569711
1993 47.437615571776156
1994 47.85543082904804
1995 46.41295871559633
1996 50.21078298695022
1997 50.37747015281757
1998 49.902007345346036
1999 49.42897826086957
2000 47.015707177641325
2001 47.5294213849498
2002 48.67695755693582
2003 48.55792955497905
2004 48.73419128693039
2005 49.456841589014225
2006 49.53909433962264
2007 45.38488160291439
2008 48.55734687780102
2009 49.42360460206882
2010 46.60163279287509
2011 43.57029213483146
2012 46.248429267074535
2013 43.47479442604856
2014 46.94603594536305
2015 50.230513159829435
2016 51.91945400149588