Year	Percent
1990	57.88
1991	57.8
1992	57.84
1993	57.81
1994	57.72
1995	57.69
1996	58
1997	58.13
1998	58.32
1999	58.56
2000	58.68
2001	59.16
2002	58.87
2003	58.76
2004	57.19
2005	57.47
2006	57.87
2007	58.94
2008	59.25
2009	59.47
2010	60.49
2011	61.99
2012	63.88
2013	66.15
2014	67.6
2015	68.43
2016	69.98
2017	71.18
2018	73.25
2019	74.39