Year	Percent
1991	4.48
1992	13.67
1993	14.46
1994	15.22
1995	14.58
1996	16.03
1997	18.06
1998	18.88
1999	20.34
2000	20.72
2001	20.38
2002	15.34
2003	16.05
2004	14.33
2005	13.9
2006	13.15
2007	12.57
2008	11.8
2009	12
2010	12.57
2011	12.31
2012	12.17
2013	11.77
2014	11.55
2015	9.57
2016	8.48
2017	8.17