Year	Percent
1991	12.86
1992	12.94
1993	12.92
1994	13.08
1995	13.24
1996	13.39
1997	13.49
1998	13.54
1999	13.56
2000	13.59
2001	13.56
2002	13.49
2003	13.44
2004	13.42
2005	13.42
2006	13.11
2007	12.82
2008	12.54
2009	12.18
2010	11.95
2011	11.81
2012	11.71
2013	11.66
2014	11.66
2015	11.64
2016	11.75
2017	11.85
2018	11.9
2019	11.9