Year	Percent
1990	70.78
1991	71.69
1992	71.72
1993	72.66
1994	73.81
1995	74.33
1996	75.15
1997	75.87
1998	76.12
1999	76.81
2000	78.04
2001	76.47
2002	78.54
2003	79.81
2004	80.75
2005	81.19
2006	82.27
2007	83.06
2008	83.99
2009	84.83
2010	85.75
2011	86.24
2012	86.93
2013	87.19
2014	87.35
2015	87.39
2016	87.47
2017	87.09
2018	86.95
2019	87.07