Year	% of total
1960	0
1961	0
1962	0
1963	0
1964	0
1965	0
1966	0
1967	0
1968	0
1969	0
1970	0.08347690176367156
1971	0.0844361451652188
1972	0.08981815504674961
1973	0.07401533174729051
1974	0.06368949497976921
1975	0.13764038100806353
1976	0.20953554820998377
1977	0.3333728921446989
1978	0.3215041510662543
1979	0.2397257003142221
1980	0.3314229212824785
1981	0.38546856249318157
1982	0.42905220869381355
1983	0.48536116070654717
1984	0.46568336917684117
1985	0.48639913387519207
1986	0.41956514957731544
1987	0.4245660075713015
1988	0.4856260462968308
1989	0.36752717391304346
1990	0.3716783725513538
1991	0.36446115968439213
1992	0.43777919591576264
1993	0.45291078815483893
1994	0.5121129631701283
1995	0.7826275997004759
1996	0.8415770195829607
1997	1.1726329257138628
1998	1.4985107967237528
1999	2.1789085538557207
2000	2.823633787643547
2001	3.610120694907473
2002	4.9842237106999505
2003	5.946065686537408
2004	6.898919942743953
2005	8.24681718461193
2006	8.860485415214729
2007	10.261762065206948
2008	12.470013955971163
2009	16.332327174177454
2010	18.59479753285063
2011	19.526777414563703
2012	22.59527389757163
2013	26.485103661461384
2014	25.859341186911028
2015	24.820009215528167