Year	Percent
1991	81.08
1992	80.55
1993	79.97
1994	79.4
1995	78.85
1996	78.28
1997	77.7
1998	77.1
1999	76.39
2000	75.71
2001	75
2002	74.26
2003	73.52
2004	72.37
2005	71.18
2006	70.72
2007	70.29
2008	69.35
2009	68.17
2010	67.07
2011	65.95
2012	64.77
2013	63.54
2014	62.33
2015	62.61
2016	62.88
2017	63.16
2018	63.4
2019	63.39
2020	62.14