Year	Percent
1990	77.87
1991	77.97
1992	78.06
1993	78.02
1994	78.01
1995	78.44
1996	78.84
1997	79.22
1998	79.58
1999	79.95
2000	80.31
2001	80.69
2002	81.07
2003	81.45
2004	81.81
2005	82.14
2006	81.98
2007	81.81
2008	81.62
2009	81.42
2010	81.22
2011	81.05
2012	80.88
2013	80.72
2014	80.41
2015	80.12
2016	79.89
2017	79.66
2018	79.47
2019	79.29
2020	76.44