Year	Percent
1991	60
1992	60.68
1993	62.05
1994	62.03
1995	61.95
1996	59.9
1997	59.82
1998	57.84
1999	54.11
2000	53.9
2001	57.7
2002	57.29
2003	58.77
2004	57.86
2005	58.44
2006	57.8
2007	57.14
2008	57.46
2009	59.26
2010	60.73
2011	61.92
2012	63.02
2013	63.16
2014	63.56
2015	64.06
2016	63.46
2017	63.04
2018	62.42
2019	61.05
2020	52.97