Year	% 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