Year	Percent
1990	57.83
1991	57.81
1992	57.8
1993	57.81
1994	57.84
1995	57.88
1996	57.81
1997	57.76
1998	57.72
1999	57.68
2000	57.65
2001	57.59
2002	57.55
2003	57.52
2004	57.49
2005	57.45
2006	57.34
2007	57.22
2008	57.11
2009	57.01
2010	56.92
2011	56.85
2012	56.79
2013	56.73
2014	56.69
2015	56.64
2016	56.6
2017	58.86
2018	59.01
2019	59.12
2020	55.73