Year	Percent
1990	66.98
1991	67.7
1992	68.41
1993	69.12
1994	69.79
1995	70.43
1996	71.01
1997	71.56
1998	72.06
1999	72.5
2000	72.88
2001	73.22
2002	73.52
2003	73.8
2004	74.11
2005	74.44
2006	74.94
2007	75.42
2008	75.87
2009	76.26
2010	76.58
2011	76.69
2012	76.77
2013	76.84
2014	76.9
2015	76.98
2016	77.04
2017	77.1
2018	77.23
2019	77.32