Year	% of total
1960	2.9473100805050114
1961	4.049153105280637
1962	4.9464138499587795
1963	5.333031035872632
1964	6.351657574485942
1965	7.359070562947326
1966	8.52798002328746
1967	9.817680119176599
1968	10.383334115328672
1969	11.590455740912496
1970	12.275807662696865
1971	13.710365598594496
1972	14.860870010195123
1973	16.411231088428163
1974	18.49395399244342
1975	17.838417464229696
1976	19.99509510890391
1977	19.666689988106068
1978	19.301695102285468
1979	18.64089959082747
1980	18.63601486602334
1981	17.6771223864911
1982	16.327757163973722
1983	15.835795188329161
1984	14.968985513102865
1985	14.483557219682108
1986	14.660243560499318
1987	14.562399496841149
1988	14.49295772468193
1989	14.728043665263431
1990	15.209708239776202
1991	15.477381232652387
1992	15.966943362363429
1993	16.224504885512932
1994	15.342784254133651
1995	15.190697306531556
1996	16.674077092740987
1997	17.84853192271427
1998	17.317422589507814
1999	18.964836244125493
2000	19.413851929822464
2001	18.70957623874672
2002	17.162923066015814
2003	16.488662633403575
2004	16.396086359758133
2005	14.621947614072232
2006	13.98137428850839
2007	12.942525797020982
2008	13.494235449290551
2009	12.343235948677336
2010	12.909006088138108
2011	12.122748470886211
2012	12.35339812088478
2013	12.43506201266419
2014	12.775282871851672
2015	13.515829012566083
2016	13.616829028225114