Year	Percent
1991	51.3
1992	51.29
1993	51.41
1994	50.55
1995	50.65
1996	50.62
1997	50.24
1998	49.93
1999	50.13
2000	49.73
2001	50.63
2002	51.75
2003	51.7
2004	51.69
2005	51.5
2006	50.92
2007	50.77
2008	50.51
2009	50.37
2010	53.12
2011	53.01
2012	52.85
2013	52.8
2014	52.93
2015	53.43
2016	53.32
2017	53.07
2018	53
2019	52.87