Year	Percent
1991	68.76
1992	68.96
1993	69.17
1994	69.24
1995	69.22
1996	69.31
1997	69.41
1998	69.42
1999	69.43
2000	69.51
2001	69.6
2002	69.59
2003	69.58
2004	69.56
2005	69.56
2006	68.48
2007	67.37
2008	66.22
2009	64.9
2010	63.66
2011	62.42
2012	61.15
2013	61.12
2014	61.09
2015	61.06
2016	61.08
2017	61.09
2018	61.04
2019	60.96
2020	58.59