Year	Percent
1990	61.18
1991	60.94
1992	60.24
1993	59.54
1994	60.2
1995	58.66
1996	58.47
1997	59.48
1998	60.48
1999	61.48
2000	62.48
2001	63.44
2002	64.39
2003	65.34
2004	66.27
2005	67.19
2006	68.12
2007	69.04
2008	69.94
2009	70.83
2010	71.72
2011	72.58
2012	73.44
2013	74.27
2014	75.09
2015	74.78
2016	74.49
2017	74.32
2018	74.02
2019	73.65