Year	Percent
1991	58.38
1992	60.24
1993	60.91
1994	62.87
1995	63.12
1996	61.38
1997	60.36
1998	59.42
1999	59.56
2000	59.72
2001	59.13
2002	56.29
2003	57.65
2004	58.25
2005	59.59
2006	60.25
2007	59.86
2008	59.23
2009	58.48
2010	58.55
2011	59.03
2012	58.53
2013	57.3
2014	57.38
2015	57.67
2016	57.13
2017	56.06
2018	55.05
2019	54.91
2020	50.64