Year	Percent
1993	22.6
1995	22.1
1996	22
2004	21.9
2005	22
2006	22.8
2007	22.7
2008	22.9
2009	22.7
2010	22.7
2011	22.2
2012	22.5
2013	22.6
2014	22.7
2015	22.8