Year	Percent
1990	2.81
1991	2.11
1992	2.13
1993	3.19
1994	3.66
1995	2.84
1996	5.07
1997	4.76
1998	4.5
1999	4
2000	4.92
2001	4.69
2002	10.69
2003	11.6
2004	11.64
2005	10.68
2006	10.42
2007	8.95
2008	8.95
2009	9.05
2010	8.88
2011	9.2
2012	8.2
2013	8.05
2014	8.4
2015	7.53
2016	7.21
2017	7.05