Year	Percent
1992	0.7
1993	0.59
1994	0.57
1995	0.54
1996	0.48
1997	0.44
1998	0.38
1999	0.37
2000	0.4
2001	0.35
2002	0.34
2003	0.3
2004	0.35
2005	0.33
2006	0.33
2007	0.34
2008	0.34
2009	0.3
2010	0.32
2011	0.35
2012	0.36
2013	0.37
2014	0.38
2015	0.33
2016	0.37
2017	0.36