Year	Percent
1990	68.95
1991	69.07
1992	69.29
1993	69.74
1994	70.09
1995	70.36
1996	70.74
1997	70.98
1998	71.14
1999	71.34
2000	71.68
2001	71.86
2002	72.13
2003	72.48
2004	72.87
2005	73.28
2006	73.94
2007	74.6
2008	75.22
2009	75.83
2010	76.28
2011	76.41
2012	76.49
2013	76.51
2014	76.5
2015	76.49
2016	76.47
2017	76.52
2018	76.54
2019	76.55