Year	Percent
1990	80.84
1991	81.49
1992	82.18
1993	82.91
1994	83.68
1995	83.26
1996	82.2
1997	81.25
1998	80.9
1999	80.6
2000	76.9
2001	80.31
2002	78.72
2003	79.37
2004	79.69
2005	79.7
2006	80.34
2007	80.9
2008	81.41
2009	81.87
2010	83.4
2011	83.81
2012	84.3
2013	83.37
2014	84.03
2015	84.13
2016	82.82
2017	80.89
2018	77.96
2019	77.6