Year	Percent
1990	77.1
1991	77.16
1992	77.12
1993	77.3
1994	77.47
1995	77.6
1996	77.53
1997	77.51
1998	77.51
1999	77.56
2000	77.5
2001	77.34
2002	76.95
2003	76.78
2004	76.56
2005	76.44
2006	76.29
2007	76.15
2008	76.03
2009	75.88
2010	75.74
2011	75.67
2012	73.69
2013	71.57
2014	70.32
2015	68.9
2016	67.29
2017	68.59
2018	69.76
2019	70.78