Year	Percent
1990	59.74
1991	59.89
1992	59.99
1993	60.06
1994	59.53
1995	58.99
1996	58.55
1997	58.17
1998	57.84
1999	57.56
2000	57.28
2001	56.79
2002	56.25
2003	56.31
2004	56.27
2005	56.13
2006	56.08
2007	55.96
2008	55.79
2009	55.64
2010	55.53
2011	55.36
2012	55.24
2013	55.17
2014	55.09
2015	55
2016	54.95
2017	54.9
2018	54.84
2019	54.78
2020	51.34