Year	Percent
1991	69.35
1992	69.39
1993	69.27
1994	69.15
1995	69.03
1996	68.89
1997	68.75
1998	68.59
1999	68.41
2000	68.26
2001	68.12
2002	67.93
2003	67.93
2004	68.64
2005	69.25
2006	69.12
2007	68.96
2008	68.76
2009	68.35
2010	68.42
2011	68.52
2012	68.63
2013	69.71
2014	69.61
2015	69.49
2016	69.36
2017	69.22
2018	69.05
2019	68.84
2020	65.25