Year	Percent
1996	18.2
1997	38.1
1998	36.9
1999	43.8
2000	46.7
2001	49.4
2002	32
2003	32.6
2004	30.1
2005	32.7
2006	32.5
2007	35.2
2008	32.8
2009	29.6
2010	32.6
2011	29.4
2012	26.5
2013	22.1
2014	18.7
2015	16.7
2016	17.1