Year	Percent
1990	50.41
1991	50.7
1992	51.01
1993	51.34
1994	51.68
1995	52.03
1996	52.36
1997	52.23
1998	52.11
1999	51.99
2000	51.88
2001	51.8
2002	51.73
2003	51.66
2004	51.57
2005	51.45
2006	51.31
2007	51.14
2008	50.93
2009	50.71
2010	50.48
2011	50.28
2012	50.11
2013	50
2014	49.92
2015	49.82
2016	49.75
2017	49.69
2018	49.71
2019	49.74