Year	Percent
1990	69.28
1991	69.12
1992	68.95
1993	68.85
1994	68.84
1995	68.77
1996	68.71
1997	68.77
1998	68.82
1999	68.98
2000	69.04
2001	69.15
2002	69.27
2003	69.44
2004	69.6
2005	69.72
2006	69.85
2007	70.09
2008	70.26
2009	70.39
2010	70.48
2011	70.67
2012	70.78
2013	70.82
2014	70.76
2015	70.71
2016	70.7
2017	70.63
2018	70.48
2019	70.33