Year	Percent
1990	53.82
1991	53.87
1992	53.92
1993	53.94
1994	53.9
1995	53.71
1996	53.46
1997	53.13
1998	52.75
1999	52.39
2000	52.13
2001	52.23
2002	52.36
2003	52.49
2004	52.56
2005	52.49
2006	52.58
2007	52.64
2008	52.71
2009	52.76
2010	52.77
2011	52.92
2012	53.04
2013	53.19
2014	53.38
2015	53.52
2016	53.86
2017	54.2
2018	54.5
2019	54.71