Year	Percent
1991	56.52
1992	57.91
1993	58.69
1994	57.45
1995	56.6
1996	55.69
1997	56.35
1998	56.42
1999	54.08
2000	54.6
2001	55.34
2002	53.01
2003	52.3
2004	54.08
2005	57.31
2006	59.28
2007	59.72
2008	60.25
2009	60.09
2010	59.25
2011	59.2
2012	58.93
2013	58.4
2014	58.34
2015	58.19
2016	57.57
2017	56.92
2018	55.93
2019	53.8
2020	48.61