Year	Percent
1991	58.03
1992	56.41
1993	54.65
1994	51.8
1995	52.07
1996	53.37
1997	52.55
1998	52.05
1999	49.89
2000	48.36
2001	48.74
2002	48.62
2003	49.92
2004	49.01
2005	49.88
2006	51.2
2007	52.21
2008	53.56
2009	51.66
2010	50.33
2011	50.73
2012	50.87
2013	50.78
2014	51.47
2015	52.77
2016	54.25
2017	55.1
2018	55.89
2019	56.24
2020	55.05