Year	Percent
1990	59.69
1991	59.66
1992	59.67
1993	59.63
1994	59.54
1995	59.42
1996	59.24
1997	59.08
1998	58.96
1999	58.84
2000	58.72
2001	58.62
2002	58.53
2003	58.48
2004	58.47
2005	58.51
2006	58.6
2007	58.76
2008	59.01
2009	57.38
2010	55.8
2011	55.99
2012	56.57
2013	57.25
2014	57.64
2015	59.09
2016	59.34
2017	60.1
2018	59.96
2019	60.13