Year	Percent
1990	57.92
1991	57.8
1992	57.75
1993	57.79
1994	58.29
1995	57.08
1996	57.4
1997	57.72
1998	57.77
1999	58.62
2000	59.55
2001	58.97
2002	58.41
2003	58.81
2004	59.22
2005	59.31
2006	59.34
2007	59.96
2008	60
2009	60.76
2010	61.27
2011	61.77
2012	61.92
2013	62.07
2014	62.2
2015	63.2
2016	62.78
2017	62.37
2018	61.97
2019	62