Year	Percent
1991	3.47
1992	6.36
1993	7.24
1994	7.52
1995	6.79
1996	8.12
1997	9.49
1998	10.36
1999	10.96
2000	11.41
2001	10.95
2002	8.21
2003	8.36
2004	7.71
2005	7.8
2006	7.48
2007	6.48
2008	5.97
2009	6.14
2010	6.54
2011	6.56
2012	6.45
2013	6.28
2014	6.31
2015	5.5
2016	4.83
2017	4.67