Year	Percent
1990	57.42
1991	57.79
1992	58.34
1993	58.45
1994	58.46
1995	59.98
1996	67.68
1997	66.83
1998	66.17
1999	65.77
2000	65.35
2001	65.94
2002	63.95
2003	62.35
2004	63.24
2005	64.39
2006	66.16
2007	68.73
2008	69.9
2009	70.43
2010	70.81
2011	71.28
2012	70.95
2013	71.07
2014	71.8
2015	71.6
2016	70.79
2017	70.39
2018	70.37
2019	69.8
2020	70.94