Year	Percent
1990	8.27
1991	7.68
1992	7.09
1993	6.48
1994	6.31
1995	6.15
1996	5.89
1997	5.73
1998	5.63
1999	5.51
2000	5.27
2001	5.07
2002	4.82
2003	4.69
2004	4.58
2005	4.44
2006	3.87
2007	3.68
2008	3.51
2009	3.22
2010	3.02
2011	2.91
2012	2.87
2013	2.76
2014	2.65
2015	2.54
2016	2.38
2017	2.31