Year	Percent
1990	68.36
1991	68.21
1992	68.05
1993	67.96
1994	67.96
1995	67.9
1996	67.84
1997	67.9
1998	67.96
1999	68.12
2000	68.18
2001	68.29
2002	68.39
2003	68.57
2004	68.72
2005	68.85
2006	68.97
2007	69.21
2008	69.37
2009	69.5
2010	69.59
2011	69.77
2012	69.87
2013	69.91
2014	69.84
2015	69.79
2016	69.77
2017	69.7
2018	69.55
2019	69.39
2020	66.35