Year	Percent
1989	30.9
1991	36.5
1995	27.3
1996	28.9
1998	32.6
1999	28.7
2000	24
2001	25.7
2002	25.9
2003	26.8
2004	22.5
2005	22.8
2006	18.8
2007	14.9
2008	19.6
2009	18.5
2010	17.9
2011	16.2
2012	14.4
2013	12.4
2014	12.2
2015	9.9
2016	10.3