Year	Percent
1990	68.58
1991	68.41
1992	68.5
1993	68.42
1994	68.39
1995	68.37
1996	68.43
1997	68.47
1998	68.6
1999	69.09
2000	69.38
2001	69.54
2002	69.77
2003	69.94
2004	70.15
2005	70.32
2006	70.74
2007	70.91
2008	71.3
2009	71.59
2010	71.67
2011	71.72
2012	71.79
2013	71.81
2014	71.85
2015	71.91
2016	71.98
2017	72.1
2018	72.22
2019	72.29