Year	Percent
1991	74.35
1992	74.05
1993	73.84
1994	73.6
1995	73.39
1996	73.18
1997	73.01
1998	72.82
1999	72.43
2000	71.95
2001	71.5
2002	71.02
2003	70.47
2004	69.94
2005	69.4
2006	68.86
2007	68.36
2008	67.9
2009	67.36
2010	66.89
2011	66.59
2012	66.22
2013	65.81
2014	65.42
2015	65.05
2016	63.12
2017	61.22
2018	61.9
2019	60.11
2020	55.6