Year	Percent
1990	51.71
1991	51.93
1992	52.03
1993	52.14
1994	52.17
1995	52.13
1996	52.31
1997	52.4
1998	52.24
1999	52.36
2000	52.52
2001	52.55
2002	52.62
2003	52.74
2004	52.91
2005	52.89
2006	53.01
2007	53.17
2008	53.17
2009	53.31
2010	53.26
2011	53.42
2012	51.92
2013	50.47
2014	49.08
2015	49.14
2016	49.25
2017	49.36
2018	49.38
2019	49.37