Year	Percent
1990	79.35
1991	79.37
1992	79.31
1993	79.26
1994	79.18
1995	79.09
1996	78.99
1997	78.9
1998	78.79
1999	78.61
2000	78.39
2001	78.19
2002	77.97
2003	77.74
2004	77.52
2005	77.33
2006	77.17
2007	77.04
2008	76.93
2009	76.84
2010	76.75
2011	76.72
2012	76.67
2013	76.62
2014	76.56
2015	76.51
2016	76.18
2017	75.8
2018	76.95
2019	75.58