Year	Percent
1990	0.26
1991	0.27
1992	0.92
1993	2.1
1994	3.08
1996	4.91
1997	8.74
1998	11.39
1999	11.91
2001	12.18
2002	12.24
2003	10.03
2004	10.24
2005	9.47
2006	10.32
2007	8.17
2008	8.39
2009	8.8
2010	7.89
2011	7.39
2012	6.54
2013	6.73
2014	5.6
2015	7.98
2016	7.54
2017	7.46