Year	Percent
1990	78.16
1991	78.23
1992	78.4
1993	78.64
1994	78.92
1995	79.22
1996	79.4
1997	79.68
1998	79.88
1999	79.87
2000	80.13
2001	80.37
2002	80.42
2003	81.08
2004	80.28
2005	79.99
2006	79.52
2007	79.05
2008	79.62
2009	81.95
2010	82.8
2011	83.27
2012	83.99
2013	83.93
2014	84.09
2015	84.55
2016	84.42
2017	84.36
2018	83.93
2019	83.47