Year	Percent
1990	62.03
1991	63.27
1992	65.31
1993	67.51
1994	70.31
1995	71.13
1996	70.56
1997	69.63
1998	69.55
1999	69.32
2000	68.9
2001	68.52
2002	68.75
2003	68.65
2004	68.48
2005	69.53
2006	70.2
2007	69.37
2008	68.48
2009	67.51
2010	67.7
2011	68.16
2012	67.52
2013	66.05
2014	65.93
2015	65.88
2016	65.02
2017	63.64
2018	62.45
2019	62.35