Year	Percent
1990	79.71
1991	79.63
1992	79.56
1993	79.46
1994	79.41
1995	79.35
1996	79.22
1997	79.1
1998	79.03
1999	78.97
2000	78.95
2001	78.81
2002	78.66
2003	78.61
2004	78.56
2005	78.5
2006	78.52
2007	78.44
2008	78.42
2009	78.54
2010	78.53
2011	78.5
2012	78.48
2013	78.51
2014	78.56
2015	78.6
2016	78.53
2017	78.46
2018	78.48
2019	78.51