Year	Percent
1991	52.52
1992	52.65
1993	52.7
1994	52.78
1995	52.87
1996	52.88
1997	52.88
1998	52.87
1999	52.82
2000	52.8
2001	52.8
2002	52.75
2003	52.73
2004	52.76
2005	52.83
2006	52.95
2007	53.06
2008	53.14
2009	53.04
2010	53.11
2011	53.24
2012	53.38
2013	53.39
2014	53.53
2015	53.59
2016	53.73
2017	53.85
2018	53.93
2019	53.98
2020	51.7