Year	Percent
1996	19.8
1999	26
2002	21.1
2003	20.2
2004	20.1
2005	20
2006	21.8
2007	20.4
2008	18.9
2009	17.4
2010	16.6
2011	15.7
2012	15.1
2013	14.3
2014	14.2