Year	Percent
1991	54.26
1992	52.81
1993	52.96
1994	55.7
1995	58.83
1996	58.88
1997	57.78
1998	55.34
1999	54.09
2000	54.2
2001	55.32
2002	56.09
2003	55.75
2004	56.12
2005	56.33
2006	58.16
2007	58.09
2008	55.84
2009	50.9
2010	49.14
2011	48.53
2012	48.08
2013	49.43
2014	51.88
2015	53.1
2016	54.12
2017	55.14
2018	56.46
2019	56.67