Year	Percent
1990	70.37
1991	70.62
1992	70.8
1993	71.08
1994	71.02
1995	70.89
1996	70.77
1997	70.59
1998	70.38
1999	70.15
2000	69.94
2001	69.78
2002	69.63
2003	69.46
2004	69.22
2005	69.11
2006	69.06
2007	68.94
2008	66.48
2009	63.92
2010	61.27
2011	61.21
2012	61.14
2013	61.03
2014	60.88
2015	60.72
2016	60.6
2017	60.48
2018	60.32
2019	60.14