Year	Percent
1990	60.18
1991	60.23
1992	59.86
1993	59.48
1994	59.14
1995	58.81
1996	59.37
1997	59.91
1998	60.45
1999	60.96
2000	61.74
2001	61.89
2002	62.04
2003	62.21
2004	62.37
2005	62.52
2006	62.69
2007	63.13
2008	63.57
2009	64
2010	64.42
2011	64.85
2012	65.28
2013	65.7
2014	66.09
2015	66.28
2016	66.46
2017	66.61
2018	66.64
2019	66.66
2020	64.84