Year	Percent
1990	59.93
1991	59.96
1992	60.01
1993	60.07
1994	60.08
1995	60.02
1996	59.59
1997	59.21
1998	58.98
1999	58.96
2000	59.13
2001	59.01
2002	59.08
2003	59.38
2004	59.84
2005	60.39
2006	60.36
2007	60.48
2008	60.8
2009	61.27
2010	61.79
2011	61.67
2012	61.63
2013	61.76
2014	62.06
2015	62.42
2016	62.06
2017	61.82
2018	61.79
2019	61.96
2020	60.8