Year	Percent
1989	18
1991	20.7
1995	12.5
1996	14.1
1998	20
1999	16.3
2000	12.2
2001	13.5
2002	14
2003	14.8
2004	10.9
2005	10.4
2006	6.9
2007	4.5
2008	6.7
2009	6.4
2010	5.5
2011	4.5
2012	4.1
2013	3.2
2014	3
2015	1.9
2016	2.2