Year	Percent
1990	68.15
1991	68.13
1992	68.29
1993	68.74
1994	69.93
1995	70.67
1996	69.92
1997	68.81
1998	67.54
1999	66.23
2000	67.24
2001	66.39
2002	66.55
2003	66.75
2004	66.81
2005	66.77
2006	66.74
2007	66.63
2008	66.5
2009	66.4
2010	66.45
2011	66.79
2012	66.44
2013	67.27
2014	65.83
2015	66.25
2016	66.25
2017	66.48
2018	66.58
2019	66.64