Year	Percent
1990	78.89
1991	78.98
1992	78.7
1993	78.53
1994	78.29
1995	78.07
1996	77.88
1997	77.7
1998	77.51
1999	77.09
2000	76.55
2001	76.09
2002	75.59
2003	74.99
2004	74.4
2005	73.79
2006	73.2
2007	72.65
2008	72.16
2009	71.63
2010	71.14
2011	70.84
2012	70.45
2013	70.02
2014	69.62
2015	69.28
2016	67.69
2017	66.16
2018	66.47
2019	64.51