Year	Percent
1990	91.9
1991	91.89
1992	91.88
1993	90.35
1994	88.77
1995	88.32
1996	87.88
1997	86.66
1998	85.81
1999	87.93
2000	88.25
2001	87.47
2002	87.84
2003	87.64
2004	87.98
2005	88.32
2006	88.62
2007	89.2
2008	88.99
2009	88.85
2010	89.17
2011	89.42
2012	89.82
2013	89.35
2014	89.71
2015	89.86
2016	90.49
2017	90.95
2018	91.3
2019	90.74