Year	% of total
1971	0
1972	0
1973	0
1974	0
1975	0
1976	0
1977	0
1978	0
1979	0
1980	0
1981	0
1982	0
1983	0
1984	0
1985	0
1986	0
1987	0
1988	0
1989	0
1990	0
1991	0
1992	0
1993	0
1994	0
1995	0
1996	0
1997	0
1998	0
1999	0.04851228978007762
2000	0.15705311250713877
2001	0.16221796195251437
2002	0.19754480033864824
2003	0.18144116122343182
2004	0.18214936247723132
2005	0.21450021450021448
2006	0.22105263157894736
2007	0.201999798000202
2008	0.2698650674662669
2009	0.43060284398157417
2010	0.9536154059809278
2011	1.2266254932235374
2012	1.579699184942442
2013	2.337187058138568
2014	2.6723376936040446
2015	3.193749051737217