Year	Percent
1990	67.92
1991	67.66
1992	67.36
1993	67
1994	66.59
1995	66.12
1996	65.64
1997	65.12
1998	64.58
1999	64.08
2000	63.65
2001	63.78
2002	63.98
2003	64.24
2004	64.54
2005	64.85
2006	65.13
2007	65.42
2008	65.72
2009	66.03
2010	66.33
2011	66.65
2012	66.97
2013	67.28
2014	67.58
2015	67.87
2016	68.15
2017	68.42
2018	68.68
2019	68.93