Year	Percent
1990	65.55
1991	66.15
1992	64.28
1993	62.25
1994	59.99
1995	59.93
1996	60.19
1997	59.64
1998	59.27
1999	59.36
2000	59.75
2001	60.46
2002	59.82
2003	60.23
2004	60.21
2005	59.57
2006	59.1
2007	58.76
2008	59.19
2009	58.72
2010	58.79
2011	58.72
2012	59.12
2013	59.2
2014	59.28
2015	59.61
2016	60.06
2017	59.98
2018	59.8
2019	59.67
2020	59.06