Year	Percent
1991	54.56
1992	53.91
1993	53.24
1994	53.16
1995	53.6
1996	53.63
1997	54.46
1998	54.92
1999	53.84
2000	53.41
2001	54.26
2002	54.56
2003	52.81
2004	55.43
2005	55.36
2006	55.76
2007	56.89
2008	56.89
2009	55.95
2010	54.96
2011	53.33
2012	52.63
2013	51.66
2014	52.15
2015	52.27
2016	52.19
2017	54.68
2018	55.87
2019	55.41
2020	54.41