Year	% of total
1960	9.087739686228936
1961	6.112702960840497
1962	4.364669421487603
1963	10.156448202959831
1964	12.834182673461388
1965	11.889367816091955
1966	14.480977576215674
1967	11.414081145584726
1968	17.337669619827295
1969	22.853996696531357
1970	27.54763312264108
1971	23.033992897006595
1972	25.655438747049992
1973	31.645084667841545
1974	22.127320762911225
1975	18.669519697374955
1976	24.088190052982398
1977	18.318327391383164
1978	14.110601141833651
1979	11.45427209948271
1980	10.842516013448842
1981	6.56823681830404
1982	4.2622950819672125
1983	2.52861577837287
1984	2.5879391436836174
1985	2.675195108214659
1986	2.506799821377826
1987	2.7470881240402982
1988	2.997512899513716
1989	2.131296802125722
1990	3.0877025212865736
1991	1.843548442727555
1992	2.4097011693373758
1993	2.2953879402085824
1994	2.6069997409760632
1995	2.259701725618802
1996	1.9056405229700317
1997	1.9920203538799581
1998	1.7002294525916741
1999	1.336078437018587
2000	0.838859037384246
2001	0.8914426872163896
2002	1.1913814955640052
2003	1.1491117804710291
2004	0.7164074785951424
2005	0.7083959083052337
2006	0.5843619399358538
2007	0.5772662933103576
2008	0.8433205909701416
2009	0.7423441424190707
2010	0.5999454595036815
2011	0.5659786941674263
2012	0.4431125818409055
2013	0.32838878987327563
2014	0.346579728023027
2015	0.30905141624269283