Year	Percent
1990	56.53
1991	56.96
1992	57.27
1993	57.37
1994	57.39
1995	57.29
1996	57.22
1997	57.27
1998	57.15
1999	57.36
2000	57.25
2001	57.24
2002	57.28
2003	57.34
2004	57.35
2005	57.34
2006	57.4
2007	57.45
2008	57.5
2009	57.3
2010	57.23
2011	57.25
2012	58.72
2013	58.91
2014	61.43
2015	62.37
2016	63.14
2017	63.37
2018	64.77
2019	66.31