Year	Percent
1990	91.39
1991	90.95
1992	90.43
1993	89.82
1994	89.14
1995	88.37
1996	87.65
1997	86.85
1998	85.97
1999	85.22
2000	84.42
2001	83.7
2002	83
2003	82.32
2004	81.69
2005	81.13
2006	80.65
2007	80.24
2008	79.9
2009	79.62
2010	79.41
2011	79.25
2012	79.13
2013	79.04
2014	78.92
2015	79.29
2016	79.59
2017	79.8
2018	79.94
2019	80