Year	Percent
1990	8.47
1991	8.45
1992	8.45
1993	8.46
1994	8.48
1995	8.49
1996	8.51
1997	7.86
1998	7.27
1999	6.72
2000	6.21
2001	5.74
2002	5.31
2003	5.42
2004	5.54
2005	5.67
2006	5.8
2007	5.94
2008	6.07
2009	6.19
2010	6.32
2011	6.45
2012	6.59
2013	6.58
2014	6.58
2015	6.58
2016	6.57
2017	6.56
2018	6.55
2019	6.54