Year	% of total
1960	6.670834077513842
1961	16.13860565365166
1962	23.999752164686566
1963	23.174612113873792
1964	33.826555353140854
1965	32.55684432283217
1966	33.13160014318955
1967	36.23882768655165
1968	40.00930133416012
1969	45.307995474948
1970	49.19053014695783
1971	55.39541639767592
1972	57.38793373862906
1973	62.357903221323554
1974	61.9345250213771
1975	57.14991288123037
1976	57.404671689856166
1977	52.43092181040022
1978	56.68124238240748
1979	56.15059302007273
1980	57.00317211157985
1981	56.30832504442482
1982	51.67082815438936
1983	50.90028815883715
1984	41.3686566167138
1985	41.799415047438224
1986	41.01908467667222
1987	45.35785609101729
1988	44.69679605361503
1989	49.626535982425224
1990	48.19162362125669
1991	47.739747034777
1992	52.10447841629691
1993	51.84145259277799
1994	50.84899886333829
1995	50.89230043309011
1996	48.90934761359744
1997	45.96388181272412
1998	42.30352250103487
1999	35.24676476827834
2000	31.81361853145687
2001	27.587221490728002
2002	31.623020048138596
2003	26.543080502169218
2004	19.50658773332612
2005	15.867807573103354
2006	14.902288334725423
2007	11.481010440526633
2008	10.032947720610984
2009	9.024225293495414
2010	7.267724995230493
2011	6.614046991830978
2012	6.353894072614011
2013	5.377393551434655
2014	5.092479397086108
2015	4.753482359125166