Year	Percent
1990	0.36
1991	0.18
1992	0.86
1993	1.54
1994	2.2
1996	3.27
1997	9.09
1998	12.17
1999	13.55
2001	13.35
2002	13.72
2003	10.85
2004	10.89
2005	10.16
2006	10.92
2007	8.63
2008	7.99
2009	9.25
2010	8.08
2011	7.22
2012	6.68
2013	6.46
2014	5.63
2015	5.51
2016	6.04
2017	5.22