Year	Percent
1990	60.57
1991	60.24
1992	60.86
1993	61.11
1994	60.66
1995	60.36
1996	59.94
1997	59.94
1998	58.83
1999	57.53
2000	56.05
2001	56.33
2002	57.8
2003	56.96
2004	57.25
2005	57.26
2006	59.01
2007	60.2
2008	61.49
2009	60.09
2010	58.99
2011	58.61
2012	59.75
2013	59.35
2014	59.23
2015	60.06
2016	60.62
2017	61.21
2018	61.78
2019	61.42
2020	61.83