Year	Percent
1990	58.48
1991	58.57
1992	58.63
1993	58.62
1994	58.56
1995	58.75
1996	59.03
1997	59.47
1998	59.95
1999	60.49
2000	61.08
2001	61.62
2002	62.2
2003	62.79
2004	63.36
2005	63.91
2006	63.83
2007	63.72
2008	63.59
2009	63.45
2010	63.31
2011	63.29
2012	63.29
2013	63.31
2014	63.82
2015	64.01
2016	65.03
2017	64.84
2018	65.05
2019	65.23
2020	61.35