Year	Percent
1990	5.34
1991	3.59
1992	4.07
1993	5.49
1994	5.46
1995	5.03
1996	7.13
1997	7.92
1998	7.64
1999	6.98
2000	7.4
2001	7.73
2002	19.18
2003	20.55
2004	20.46
2005	19.72
2006	19.08
2007	16.98
2008	16.44
2009	16.56
2010	16.44
2011	16.44
2012	15.51
2013	15.26
2014	15.36
2015	14.76
2016	14.56
2017	13.96