Year	Percent
1990	58.17
1991	58.45
1992	58.64
1993	58.78
1994	58.93
1995	59.06
1996	59.12
1997	59.15
1998	59.18
1999	59.19
2000	59.19
2001	59.21
2002	59.22
2003	59.23
2004	59.26
2005	59.31
2006	59.39
2007	59.46
2008	59.55
2009	59.67
2010	59.82
2011	60.01
2012	60.22
2013	60.24
2014	60.34
2015	60.37
2016	60.48
2017	60.53
2018	60.55
2019	60.54