Year	Percent
1991	10.07
1992	10.01
1993	9.93
1994	9.86
1995	9.82
1996	9.82
1997	9.8
1998	9.78
1999	9.7
2000	9.64
2001	9.59
2002	9.47
2003	9.36
2004	9.29
2005	9.26
2006	9.27
2007	9.31
2008	9.34
2009	9.14
2010	9.03
2011	8.96
2012	8.83
2013	8.7
2014	8.67
2015	8.58
2016	8.52
2017	8.46
2018	8.42
2019	8.43