Year	Percent
1992	1.1
1993	0.94
1994	0.84
1995	0.84
1996	0.72
1997	0.67
1998	0.61
1999	0.53
2000	0.58
2001	0.48
2002	0.51
2003	0.42
2004	0.45
2005	0.45
2006	0.44
2007	0.46
2008	0.47
2009	0.39
2010	0.41
2011	0.47
2012	0.46
2013	0.49
2014	0.43
2015	0.38
2016	0.42
2017	0.43