Year	Percent
1991	75.66
1992	75.72
1993	75.62
1994	75.59
1995	75.92
1996	76.21
1997	76.49
1998	76.75
1999	76.98
2000	77.51
2001	78.05
2002	78.55
2003	79.07
2004	79.59
2005	80.09
2006	80.02
2007	79.93
2008	79.79
2009	79.51
2010	79.33
2011	79.18
2012	79.04
2013	78.9
2014	78.63
2015	78.36
2016	78.15
2017	77.97
2018	77.82
2019	77.67
2020	74.3