Year	Percent
1991	60.26
1992	60.45
1993	60.47
1994	60.35
1995	60.35
1996	60.2
1997	60.14
1998	60.34
1999	60.25
2000	60.19
2001	60.08
2002	59.93
2003	59.45
2004	59.52
2005	59.54
2006	59.47
2007	59.8
2008	59.58
2009	59.86
2010	59.95
2011	60.64
2012	60.24
2013	59.98
2014	60.55
2015	60.3
2016	60.56
2017	58.15
2018	58.18
2019	58.69
2020	55.11