Year	Percent
1990	13.8
1991	10
1992	11.2
1993	10.4
1994	9.8
1995	9.4
1996	9.98
1997	9.48
1998	13.63
1999	12.24
2000	13.06
2001	10.55
2002	10.73
2003	9.92
2004	9.35
2005	7.96
2006	10.48
2007	10.29
2008	10.77
2009	10.63
2010	10.42
2011	10.76
2012	8.86
2013	9.07
2014	8.92
2017	7.99