Year	Percent
1990	64.07
1991	64.1
1992	64.13
1993	64.14
1994	64.1
1995	64.01
1996	63.81
1997	63.54
1998	63.21
1999	62.86
2000	62.5
2001	62.27
2002	62.05
2003	61.85
2004	61.67
2005	61.53
2006	61.71
2007	61.89
2008	62.06
2009	62.21
2010	62.35
2011	62.52
2012	62.73
2013	62.95
2014	63.13
2015	63.26
2016	63.4
2017	63.5
2018	63.73
2019	63.89