Year	Percent
1990	71.56
1991	71.61
1992	71.51
1993	71.36
1994	71.08
1995	70.83
1996	70.5
1997	70.12
1998	69.79
1999	69.47
2000	69.07
2001	68.74
2002	68.4
2003	68.1
2004	67.58
2005	67.18
2006	67.1
2007	66.82
2008	66.51
2009	66.27
2010	65.96
2011	65.74
2012	65.44
2013	65.17
2014	64.92
2015	64.73
2016	64.56
2017	64.4
2018	64.26
2019	64.05
2020	62.51