Year	Percent
1990	68.93
1991	69.16
1992	69.03
1993	68.51
1994	67.54
1995	66.39
1996	65.79
1997	64.77
1998	64.38
1999	63.88
2000	64.78
2001	65.42
2002	64.47
2003	64.04
2004	63.67
2005	64.27
2006	63.35
2007	63.18
2008	63.85
2009	64.68
2010	65.58
2011	65.98
2012	66.71
2013	67.21
2014	68.08
2015	68.38
2016	69.1
2017	69.85
2018	70.41
2019	70.85