Year	Percent
1990	60.21
1991	60.18
1992	60.18
1993	60.2
1994	60.25
1995	60.16
1996	60.05
1997	59.95
1998	59.84
1999	59.74
2000	59.66
2001	59.79
2002	59.93
2003	60.09
2004	60.25
2005	60.42
2006	59.57
2007	58.73
2008	57.93
2009	57.14
2010	56.37
2011	55.42
2012	54.51
2013	54.09
2014	53.68
2015	53.29
2016	52.9
2017	52.52
2018	52.15
2019	52.13