Year	Percent
1989	62
1990	64.3
1991	56.3
1992	52.3
1993	45.9
1994	46.2
1995	48.5
1996	50.7
1997	40.2
1998	42
1999	43.2
2001	35
2002	40
2003	45
2004	44.2
2005	41.4
2006	36.6
2007	31.9
2008	30.3
2009	27.3
2010	29.4
2011	31.7
2012	36.1
2013	32.9
2014	31.8
2015	32.2
2016	30