Year	Percent
1990	61.36
1991	61.49
1992	61.24
1993	60.65
1994	59.69
1995	58.56
1996	57.9
1997	56.89
1998	56.43
1999	55.68
2000	56.28
2001	56.61
2002	55.57
2003	54.97
2004	54.55
2005	55.08
2006	54.2
2007	54.03
2008	54.59
2009	55.25
2010	55.92
2011	56.06
2012	56.36
2013	56.43
2014	56.79
2015	56.62
2016	56.8
2017	57.06
2018	57.01
2019	56.89
2020	56.58