Year	Percent
1991	54.38
1992	54.32
1993	54.23
1994	54.2
1995	54.17
1996	53.99
1997	53.83
1998	53.71
1999	53.59
2000	53.54
2001	53.52
2002	53.97
2003	53.78
2004	53.55
2005	53.28
2006	53.33
2007	52.85
2008	53.56
2009	53.45
2010	53.86
2011	53.2
2012	53.36
2013	54.4
2014	54.59
2015	54.93
2016	54.66
2017	54.92
2018	54.5
2019	54.2
2020	52.33