Year	Percent
1990	69.6
1991	69.95
1992	70.79
1993	69.16
1994	69.32
1995	71.48
1996	81.58
1997	81.66
1998	81.34
1999	81.59
2000	81.78
2001	82.54
2002	81.23
2003	80.66
2004	81.86
2005	83.26
2006	85.25
2007	87.25
2008	88.43
2009	88.49
2010	88.29
2011	89.29
2012	89.56
2013	89.62
2014	90.28
2015	90.28
2016	89.77
2017	89.36
2018	89.58
2019	89.59