Year	Percent
1990	59.88
1991	60.31
1992	60.74
1993	61.22
1994	61.28
1995	61.28
1996	61.25
1997	60.85
1998	60.47
1999	60.1
2000	60.29
2001	60.51
2002	60.72
2003	61.37
2004	61.68
2005	61.93
2006	62.15
2007	62.73
2008	63.46
2009	63.92
2010	64.21
2011	64.23
2012	63.86
2013	64.82
2014	65.22
2015	64.78
2016	64.38
2017	65.1
2018	65.25
2019	66.07