Year	Percent
1991	55.81
1992	55.43
1993	54.99
1994	54.66
1995	54.36
1996	54.87
1997	55.38
1998	55.88
1999	56.33
2000	57.06
2001	57.21
2002	57.33
2003	57.48
2004	58.37
2005	59.16
2006	59.36
2007	60.05
2008	59.63
2009	58.78
2010	59.38
2011	60.67
2012	61.88
2013	62.23
2014	63.1
2015	63.17
2016	63.87
2017	64.41
2018	63.18
2019	63.23
2020	61.07