Year	Percent
1991	55.03
1992	56.16
1993	57.23
1994	58.3
1995	60.07
1996	61.74
1997	63.39
1998	64.11
1999	65.09
2000	63.51
2001	66.51
2002	68.27
2003	69.66
2004	71.26
2005	69.13
2006	72.37
2007	74.85
2008	74.98
2009	75.46
2010	76.47
2011	76.01
2012	76.1
2013	75.31
2014	74.77
2015	73.61
2016	72.89
2017	74.5
2018	75.1
2019	75.5
2020	61.1