Annual % of total
1960 2.0983748411346372
1961 2.8205562872455565
1962 3.1218542070760398
1963 2.871948006323555
1964 2.9097860139117504
1965 2.865004012464696
1966 3.053056224390656
1967 3.2450122230108036
1968 3.7210410906664126
1969 4.0178531815398815
1970 4.300868693618443
1971 4.826853386409953
1972 5.50360041496308
1973 6.025781172361902
1974 6.4872371379447165
1975 8.072959401358757
1976 7.669043146527027
1977 8.401522141980157
1978 8.687268483280054
1979 9.166886113844576
1980 9.723250177775842
1981 11.025177825448797
1982 11.064108374880394
1983 12.576684454857045
1984 13.241600173695922
1985 13.936938008250928
1986 14.450636185549365
1987 13.94752435813994
1988 14.081495931114658
1989 13.83353202354244
1990 16.7223181129747
1991 17.15742572696945
1992 17.68049829110834
1993 19.07305810660029
1994 18.473385392475617
1995 19.22916174633814
1996 20.345093216653982
1997 19.98501726346272
1998 20.076242982318064
1999 20.807046933333336
2000 21.947570731968703
2001 22.81974314068885
2002 23.13004930355363
2003 23.8962209425751
2004 24.329591744939805
2005 24.673916285909353
2006 24.42068057050592
2007 24.289037502411066
2008 25.501420116691325
2009 25.61610852623008
2010 28.00152986147037
2011 25.436905825562917
2012 26.026508786013736
2013 26.53926298903841
2014 24.514099103536598