Year	% of total
1960	2.995759678396387
1961	3.3587894215811063
1962	3.9424280350438052
1963	4.066355821993847
1964	4.621557211378925
1965	5.467382598119197
1966	5.8499985487475685
1967	6.224277652849082
1968	7.051775894588635
1969	7.045454545454547
1970	8.4555900845559
1971	8.729499081043747
1972	9.111014792340434
1973	10.30732138376444
1974	10.57360931983001
1975	11.05003124511795
1976	11.39057876454263
1977	11.843107054406707
1978	12.197957953879973
1979	12.628037259256805
1980	12.117672131406335
1981	11.891795215738878
1982	10.998106619882227
1983	10.632700372483136
1984	9.297353030661574
1985	9.237816411454137
1986	9.397015408258179
1987	9.054159476135316
1988	8.908147575625518
1989	9.31745811989478
1990	9.752280852035863
1991	9.789303813667775
1992	10.614297405131492
1993	10.901229288994827
1994	11.696623693892569
1995	12.466721470588237
1996	13.115005065856128
1997	13.860181063749527
1998	15.372355139599888
1999	16.36015114246877
2000	16.830179567819822
2001	17.899106607629427
2002	18.1448082010582
2003	17.780700369499495
2004	18.797900735537738
2005	18.920916874066698
2006	19.030246107803496
2007	19.543213134633184
2008	20.768407498702647
2009	20.995875664401535
2010	20.923896857270353
2011	21.400573746740076
2012	21.003502554804683
2013	19.109995307210138
2014	19.622184503394692
2015	20.294412385400452
2016	22.103052312003733