Year	Percent
1970	0.35639
1971	0.60853
1972	0.64945
1973	0.62947
1974	0.60523
1975	0.59615
1976	0.30981
1977	0.2701
1978	0.28094
1979	0.29409
1980	0.47706
1981	0.5456
1982	0.47176
1983	0.53901
1984	0.78596
1985	1.01051
1986	0.61459
1987	0.96678
1988	1.63538
1989	2.86615
1990	3.31546
1991	2.7436
1992	1.74106
1993	1.61429
1994	1.27356
1995	0.57949
1996	1.09837
1997	2.0134
1998	2.42319
1999	0.91599
2000	6.16201
2001	5.03302
2002	0.44384
2003	6.2655
2004	1.31984
2005	2.24471
2006	6.32822
2007	2.50914
2008	2.98517
2009	2.28882
2010	3.54833
2011	4.00893
2012	10.15705
2013	4.77937
2014	5.74344
2015	1.2569
2016	4.59215
2017	4.60675