Year	Percent
1993	26.3
1996	26.2
1997	21.1
1998	26.2
1999	37.3
2000	32.1
2001	25.4
2002	20.8
2003	19.8
2004	17.4
2005	14.7
2006	11.6
2007	8.3
2008	5.2
2009	4.9
2010	4
2011	3.2
2012	2.9
2013	2.5
2014	2.4
2015	2.7