Year	Percent
1991	54.98
1992	55.06
1993	55.1
1994	55.15
1995	55.23
1996	55.31
1997	55.42
1998	55.52
1999	55.59
2000	55.7
2001	54.13
2002	54.91
2003	53.79
2004	54.1
2005	53.75
2006	55.44
2007	55.38
2008	55.96
2009	53.47
2010	55.05
2011	56.06
2012	56.43
2013	56.32
2014	56.97
2015	58.88
2016	59.44
2017	60.41
2018	61.86
2019	62.71
2020	56.24