Year	Percent
1991	63.98
1992	63.93
1993	63.72
1994	63.5
1995	63.18
1996	62.94
1997	62.75
1998	62.44
1999	62.02
2000	61.68
2001	61.54
2002	62.03
2003	62.51
2004	62.96
2005	63.37
2006	64
2007	64.46
2008	61.05
2009	57.33
2010	53.64
2011	53.61
2012	53.54
2013	53.43
2014	53.31
2015	53.06
2016	52.82
2017	52.52
2018	52.14
2019	51.69