Year	Percent
1990	83.27
1991	83.18
1992	83.12
1993	82.93
1994	82.66
1995	82.44
1996	82.22
1997	82.07
1998	80.85
1999	79.43
2000	80.13
2001	80.94
2002	81.66
2003	82.3
2004	82.92
2005	82.86
2006	82.94
2007	83.03
2008	83.13
2009	83.21
2010	83.27
2011	83.42
2012	83.52
2013	83.69
2014	83.8
2015	83.88
2016	83.99
2017	84.01
2018	83.97
2019	83.98