Year	Percent
1991	73.15
1992	72.1
1993	71.22
1994	70.52
1995	69.9
1996	70.1
1997	70.2
1998	69.2
1999	68.13
2000	67.12
2001	66.08
2002	64.99
2003	63.96
2004	63.7
2005	63.4
2006	63.12
2007	62.8
2008	62.4
2009	61.72
2010	61.22
2011	60.75
2012	60.26
2013	59.77
2014	59.33
2015	58.87
2016	58.59
2017	58.26
2018	57.86
2019	57.44