Year	Percent
1980	1.2
1986	0
1987	0.9
1991	4.4
1992	4.9
1993	5.8
1994	5.5
1995	8.6
1996	9.5
1997	8.8
1998	10.1
1999	10.7
2000	12.6
2001	17.3
2002	26.2
2003	15.5
2004	12.1
2005	10
2006	8
2007	6.9
2008	6.2
2009	6
2010	3.7
2011	2.6
2012	2.7
2013	2.4
2014	2.8
2016	2.4