Year	Percent
1990	67.92
1991	67.74
1992	67.55
1993	67.24
1994	67.36
1995	67.48
1996	67.82
1997	67.91
1998	67.9
1999	68.14
2000	68.51
2001	68.86
2002	69.33
2003	69.95
2004	70.59
2005	71.95
2006	73.1
2007	74.4
2008	75.23
2009	76.3
2010	75.45
2011	75.58
2012	75.7
2013	75.82
2014	75.91
2015	76.09
2016	76.15
2017	76.28
2018	76.44
2019	76.57