Year	Percent
1990	66.72
1991	67.23
1992	67.68
1993	68.14
1994	68.64
1995	69.19
1996	69.73
1997	70.17
1998	70.16
1999	70.38
2000	70.6
2001	70.9
2002	70.23
2003	70.36
2004	70.42
2005	70.75
2006	71.41
2007	72.06
2008	73.06
2009	72.95
2010	73.56
2011	73.86
2012	74.7
2013	74.79
2014	75.72
2015	76.64
2016	76.66
2017	77.02
2018	77.02
2019	77.42