Year	Percent
1991	55.05
1992	54.94
1993	54.77
1994	54.62
1995	54.45
1996	54.17
1997	53.85
1998	53.48
1999	53.05
2000	52.67
2001	52.38
2002	52.06
2003	51.79
2004	51.6
2005	51.48
2006	51.72
2007	51.98
2008	52.19
2009	52.2
2010	52.34
2011	52.44
2012	52.56
2013	52.67
2014	52.79
2015	52.8
2016	52.79
2017	52.76
2018	52.95
2019	53.1
2020	49.39