Year	% of total
1960	6.7088545376312245
1961	7.318675156631225
1962	7.7604208666084435
1963	8.177843747404214
1964	9.925439954764673
1965	10.406892655406637
1966	11.144393303316209
1967	12.156374256574809
1968	13.190526260428365
1969	15.944349175033034
1970	18.529637052856206
1971	21.500780954299834
1972	23.638870053244997
1973	25.181125335738187
1974	23.596204999416564
1975	22.070050108316842
1976	22.94470374098284
1977	22.44388183312914
1978	22.092943891189424
1979	20.01983471511633
1980	17.380068044736852
1981	15.679474952459197
1982	13.598913570671309
1983	12.131146459080998
1984	10.81851477265306
1985	8.790239220087848
1986	8.96125547273905
1987	8.555081483243026
1988	9.148035421335704
1989	9.805389652976812
1990	8.385158414785106
1991	8.358798834133246
1992	8.28677407156985
1993	7.7339015337999335
1994	7.674899048275849
1995	7.229463256826299
1996	6.893221226395656
1997	6.833735803954689
1998	6.959724507754064
1999	6.723159748088152
2000	6.153620233858216
2001	6.137632294580599
2002	5.90174658639066
2003	6.200241595458966
2004	5.60932584247041
2005	5.427159505384359
2006	4.587779417331263
2007	4.612159374831674
2008	4.1877302922460435
2009	3.680626594829929
2010	3.325240547126539
2011	3.500035316133337
2012	3.813467584770887
2013	3.279671145886647
2014	3.1431041794529038
2015	2.984012095891407