Year	Percent
1998	30.6
2000	42.2
2001	36.4
2002	34.2
2003	28.1
2004	13.6
2005	15.4
2006	9.9
2007	9.9
2008	4
2009	2.1
2010	4.1
2011	1.8
2012	2.9
2013	3.3
2014	1.3
2015	2.5
2016	1.4