Year	Percent
1990	67.99
1991	68.06
1992	68.14
1993	68.24
1994	68.37
1995	68.41
1996	68.44
1997	68.46
1998	68.49
1999	68.51
2000	68.53
2001	68.71
2002	68.89
2003	69.07
2004	69.26
2005	69.45
2006	68.79
2007	68.13
2008	67.49
2009	66.86
2010	66.25
2011	65.45
2012	64.68
2013	64.51
2014	64.33
2015	64.16
2016	63.97
2017	63.78
2018	63.59
2019	63.66