Year	Percent
1990	6.26
1991	13
1992	11.47
1993	13.89
1994	12.01
1995	11.74
1996	11.38
1997	11.95
1998	10.28
1999	9.72
2000	8.34
2001	8.03
2002	7.8
2003	7.62
2004	7.31
2005	7.17
2006	6.73
2007	6.68
2008	6.53
2009	6.47
2010	6.5
2011	6.17
2012	6.12
2013	5.75
2014	5.54
2015	5.31
2016	4.89
2017	4.7