Year	Percent
1991	57.25
1992	56.9
1993	54.86
1994	53.99
1995	49.45
1996	50.7
1997	52.49
1998	54.07
1999	53.12
2000	52.58
2001	51.02
2002	49.16
2003	52.23
2004	53.87
2005	54.82
2006	55.96
2007	56.26
2008	55.95
2009	55.79
2010	55.74
2011	56.28
2012	56.13
2013	55.95
2014	55.36
2015	55.45
2016	55.51
2017	55.53
2018	55.73
2019	55.55
2020	49.44