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
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	0.2275636467074385
1987	0.20939972080037225
1988	0.2834569688197335
1989	0.3273896521484946
1990	0.2645578720345076
1991	0.26019080659150046
1992	0.2122229684351914
1993	0.22025854157379973
1994	0.19811297392337981
1995	0.18160246010799294
1996	0.18391455047039681
1997	0.7691952323754967
1998	3.7093980077955826
1999	7.909707460269258
2000	11.080954609265326
2001	11.555128494988319
2002	13.089257577161925
2003	13.80709783265694
2004	15.28743645112475
2005	13.749642418429334
2006	17.63073497399425
2007	21.96424869640095
2008	21.930633265513734
2009	18.042688316364945
2010	17.135286837380377
2011	23.555059825593187
2012	21.98581560283688
2013	19.014602374198972
2014	13.459666686530403
2015	17.540812782216047