Year	Percent
1990	52.59
1991	52.48
1992	52.48
1993	52.44
1994	52.51
1995	52.37
1996	52.16
1997	51.96
1998	51.73
1999	51.51
2000	51.32
2001	51.05
2002	50.85
2003	50.69
2004	50.55
2005	50.41
2006	50.17
2007	49.93
2008	49.69
2009	49.49
2010	49.34
2011	49.17
2012	49.06
2013	49
2014	48.97
2015	48.98
2016	49.06
2017	49.16
2018	49.28
2019	49.42