Year	Percent
1990	50.78
1991	50.64
1992	50.53
1993	50.47
1994	50.48
1995	50.58
1996	50.62
1997	50.75
1998	50.98
1999	51.25
2000	51.54
2001	51.86
2002	52.22
2003	52.61
2004	53.01
2005	53.42
2006	53.56
2007	53.7
2008	53.87
2009	54.06
2010	54.24
2011	54.32
2012	54.39
2013	54.46
2014	54.51
2015	54.57
2016	54.56
2017	54.56
2018	54.58
2019	54.58
2020	52.73