Year	Percent
1998	39.1
1999	34.5
2000	27.2
2001	15.3
2002	11
2003	9.1
2004	4.5
2005	2.5
2006	1.1
2007	1.1
2008	0.5
2009	0.5
2010	0.2
2011	0.1
2012	0.1
2013	0
2014	0
2015	0
2016	0