Year	Percent
1990	78.51
1991	78.5
1992	78.53
1993	78.66
1994	78.61
1995	78.47
1996	78.4
1997	78.33
1998	78.26
1999	78.17
2000	78.07
2001	78.04
2002	77.92
2003	77.86
2004	77.76
2005	77.66
2006	77.68
2007	77.68
2008	77.7
2009	77.79
2010	77.84
2011	77.96
2012	78.02
2013	78.07
2014	78.09
2015	78.09
2016	78.12
2017	78.09
2018	78.03
2019	77.93