Year	Percent
1990	60.15
1991	60.2
1992	60.35
1993	60.32
1994	60.17
1995	59.93
1996	60.02
1997	59.88
1998	59.71
1999	59.54
2000	59.46
2001	59.43
2002	59.36
2003	59.45
2004	59.28
2005	59.17
2006	59.21
2007	59.22
2008	59.24
2009	59.08
2010	58.92
2011	59.03
2012	59.06
2013	60
2014	60
2015	59.89
2016	59.73
2017	59.55
2018	59.33
2019	59.11