Year	Percent
1990	78.94
1991	79.01
1992	79.08
1993	79.03
1994	79.01
1995	79.49
1996	79.94
1997	80.37
1998	80.79
1999	81.21
2000	81.62
2001	82.06
2002	82.49
2003	82.92
2004	83.33
2005	83.71
2006	83.6
2007	83.48
2008	83.35
2009	83.2
2010	83.06
2011	82.93
2012	82.81
2013	82.7
2014	82.41
2015	82.12
2016	81.91
2017	81.69
2018	81.51
2019	81.34