Year	Percent
1990	61.45
1991	61.16
1992	60.86
1993	60.55
1994	60.23
1995	59.91
1996	59.6
1997	59.29
1998	58.98
1999	58.65
2000	58.32
2001	58.42
2002	58.52
2003	58.62
2004	58.72
2005	58.83
2006	58.83
2007	58.88
2008	58.78
2009	58.79
2010	58.41
2011	58.55
2012	58.53
2013	58.58
2014	58.57
2015	58.49
2016	58.5
2017	58.51
2018	58.55
2019	58.46