Year	% of total
1960	0
1961	0.01899711085605731
1962	0.0728485987572029
1963	0.037519932464121566
1964	0.06358678373156594
1965	0.06824346000174983
1966	0.14998613335748204
1967	0.6677641620513715
1968	0.8736476024161354
1969	2.198394286045072
1970	2.1031767879755545
1971	1.8994710449840948
1972	2.7529699520933497
1973	3.233854767705261
1974	3.7020915959781138
1975	6.289704771086849
1976	7.00792315559426
1977	9.683067599570945
1978	9.793648738542862
1979	11.134945773173387
1980	11.920272762362224
1981	14.010651284803213
1982	15.899288413595979
1983	16.37193011891529
1984	20.72936393281045
1985	26.633049024127864
1986	25.00685111332987
1987	26.717024810214397
1988	28.663392486689126
1989	29.0046412162247
1990	27.84040902035972
1991	27.477016792764815
1992	29.756854397457616
1993	29.335849504389582
1994	28.694128959168324
1995	28.73254081161531
1996	29.05731163211311
1997	31.08112793356338
1998	29.26345326997058
1999	30.7674488050747
2000	29.63518214683224
2001	29.43961531983928
2002	28.3256064912347
2003	27.34578853981839
2004	27.33818247273382
2005	26.478564468983436
2006	26.43599501842802
2007	22.17803469667631
2008	23.407894322015196
2009	22.871148506863108
2010	22.432143866016155
2011	17.78096530463022
2012	15.946309069162668
2013	15.371003799698235
2014	15.617151548868216
2015	14.319925986829274