Year	Percent
1990	56.86
1991	56.64
1992	56.33
1993	55.97
1994	55.59
1995	55.26
1996	55.09
1997	54.98
1998	54.96
1999	55.04
2000	55.19
2001	55.33
2002	55.49
2003	55.65
2004	55.9
2005	56.18
2006	56.71
2007	57.31
2008	57.84
2009	58.35
2010	58.71
2011	58.87
2012	58.98
2013	59
2014	58.91
2015	58.77
2016	58.6
2017	58.36
2018	58.08
2019	57.77
2020	55.36