Year	% of total
1960	4.840595496145999
1961	6.187240536250862
1962	8.008105299447354
1963	9.44004170007713
1964	12.684664408838387
1965	13.579637473466692
1966	14.483377327992574
1967	15.271905979989636
1968	16.56746920769376
1969	19.478129811976125
1970	20.939439893951416
1971	22.584567982678717
1972	23.727145011284666
1973	25.329545692269654
1974	23.382229269536563
1975	21.08468879392385
1976	23.24301512422805
1977	19.49470314006829
1978	20.50305848241648
1979	19.975307970285236
1980	19.22826626642332
1981	16.869097262936
1982	14.118719979097738
1983	11.626713370153118
1984	8.633135145063898
1985	7.86164603191776
1986	8.000290821709891
1987	7.984164985795145
1988	7.07163743052595
1989	8.160472645458732
1990	8.389856544223566
1991	8.870153824737246
1992	9.272469340032735
1993	8.648194573877435
1994	8.617855602993863
1995	8.818727709988435
1996	8.2927468336465
1997	8.02436760231867
1998	8.169734840556265
1999	7.522882067094709
2000	6.425280659971339
2001	6.114091292535298
2002	6.5696098035258945
2003	5.942404002811716
2004	4.95247441284103
2005	4.738551594414937
2006	4.413755045633698
2007	3.69609821546918
2008	3.418465612509035
2009	3.298054776798403
2010	2.7767536349928053
2011	2.4295827259663416
2012	2.461128124345939
2013	2.05541281373615
2014	1.9875745606036732
2015	2.055826253234948