Year	Percent
1991	64.8
1992	64.47
1993	64.01
1994	65.16
1995	66.26
1996	67.32
1997	68.61
1998	69.84
1999	69.39
2000	69
2001	68.65
2002	68.2
2003	67.76
2004	67.36
2005	66.96
2006	68.9
2007	70.5
2008	71.74
2009	69.19
2010	66.55
2011	68.19
2012	69.5
2013	68.88
2014	68.25
2015	67.57
2016	66.87
2017	66.16
2018	65.7
2019	65.62
2020	65.17