Year	Percent
1990	57.84
1991	58.97
1992	60.91
1993	63.05
1994	65.97
1995	66.87
1996	66.22
1997	65.25
1998	65.23
1999	65.02
2000	64.59
2001	64.16
2002	64.37
2003	64
2004	63.68
2005	64.85
2006	65.68
2007	65.13
2008	64.53
2009	63.85
2010	64.08
2011	64.53
2012	63.92
2013	62.5
2014	62.4
2015	62.38
2016	61.57
2017	60.2
2018	59.06
2019	58.86
2020	54.98