Year	Percent
1990	81.5
1991	81.37
1992	81.85
1993	81.76
1994	81.76
1995	81.94
1996	81.86
1997	82.01
1998	81.99
1999	82.09
2000	81.98
2001	82.22
2002	81.75
2003	81.65
2004	82.29
2005	81.75
2006	81.18
2007	80.59
2008	79.98
2009	79.35
2010	78.71
2011	78.05
2012	77.37
2013	76.67
2014	75.96
2015	76.7
2016	76.65
2017	76.65
2018	76.66
2019	76.63