Year	Percent
1991	70.83
1992	70.45
1993	70.04
1994	69.63
1995	69.22
1996	69.08
1997	68.98
1998	68.93
1999	68.93
2000	68.81
2001	68.68
2002	68.83
2003	69.03
2004	68.72
2005	68.47
2006	68.37
2007	67.9
2008	67.86
2009	67.62
2010	66.02
2011	64.2
2012	62.47
2013	62.43
2014	60.96
2015	64.32
2016	64.67
2017	65.04
2018	65.4
2019	65.74
2020	62.85