Year	Percent
1990	61.77
1991	61.82
1992	62.08
1993	62.4
1994	62.48
1995	62.51
1996	62.85
1997	63.44
1998	63.62
1999	64.1
2000	64.57
2001	64.65
2002	65.78
2003	65.49
2004	65.35
2005	66.47
2006	67.92
2007	69.77
2008	70.59
2009	71.71
2010	72.94
2011	74.86
2012	77.47
2013	79.61
2014	80.95
2015	81.6
2016	82.97
2017	84.2
2018	85.55
2019	87.14