Year	Percent
1990	79.02
1991	79.08
1992	79.08
1993	79.07
1994	79.03
1995	78.97
1996	79.03
1997	79.07
1998	79.05
1999	79.12
2000	79.2
2001	79.28
2002	79.36
2003	79.45
2004	79.55
2005	79.58
2006	79.63
2007	79.66
2008	79.64
2009	79.65
2010	79.6
2011	79.61
2012	77.5
2013	75.16
2014	72.57
2015	72.49
2016	72.41
2017	72.34
2018	72.24
2019	72.15
2020	71.82