Year	Percent
1990	62.51
1991	59.97
1992	57.41
1993	57.54
1994	57.68
1995	55.62
1996	55.8
1997	55.96
1998	59.51
1999	57.89
2000	56.92
2001	56.8
2002	56.7
2003	56.61
2004	56.5
2005	56.37
2006	56.28
2007	56.15
2008	55.98
2009	55.78
2010	54.64
2011	54.25
2012	53.44
2013	54.85
2014	53.93
2015	54.77
2016	55.01
2017	55.07
2018	52.94
2019	52.5
2020	51.13