Year	Percent
1989	42.2
1990	44.3
1991	33.4
1992	28.7
1993	23.6
1994	26.7
1995	27.7
1996	30.4
1997	21.2
1998	25.9
1999	26.5
2001	20.6
2002	23.4
2003	28.1
2004	27.2
2005	26.5
2006	22.5
2007	17.2
2008	16.5
2009	13.8
2010	15
2011	17.1
2012	19.6
2013	17.3
2014	15.9
2015	16.2
2016	16