Year	Percent
1990	52.56
1991	52.6
1992	52.63
1993	52.64
1994	52.58
1995	52.37
1996	52.11
1997	51.76
1998	51.36
1999	50.98
2000	50.7
2001	50.75
2002	50.81
2003	50.88
2004	50.89
2005	50.77
2006	50.79
2007	50.8
2008	50.83
2009	50.84
2010	50.81
2011	50.91
2012	50.98
2013	51.08
2014	51.23
2015	51.35
2016	51.65
2017	51.96
2018	52.24
2019	52.44
2020	50.86