Year	Percent
1986	28.4
1989	54.7
1992	40.7
1996	32
1997	29.6
2000	30.2
2001	30.2
2002	31.6
2003	39.6
2004	47
2005	37.4
2006	34.5
2007	34.1
2008	35.2
2009	32.4
2010	32.5
2011	30.4
2012	31.6
2013	30.8
2014	26.5
2015	22.7
2016	21