Year	Percent
1991	56.46
1992	55.28
1993	53.85
1994	53.42
1995	53.44
1996	52.85
1997	52.41
1998	52.44
1999	53.16
2000	53.46
2001	53.45
2002	52.94
2003	52.24
2004	51.41
2005	51.93
2006	52.81
2007	54.06
2008	54.75
2009	54.76
2010	55.29
2011	56.51
2012	56.72
2013	57.08
2014	57.24
2015	57.3
2016	57.83
2017	58.25
2018	58.77
2019	59.32
2020	57.96