Year	Percent
1990	83.99
1991	83.06
1992	81.23
1993	79.28
1994	78.32
1995	79.06
1996	79.01
1997	78.52
1998	78.21
1999	78.5
2000	77.74
2001	78.05
2002	77.8
2003	77.82
2004	77.6
2005	78.25
2006	78.81
2007	79.23
2008	79.39
2009	78.86
2010	78.96
2011	79.7
2012	80.07
2013	80.99
2014	81.53
2015	81.88
2016	82.25
2017	82.74
2018	82.97
2019	83.13