Year	Percent
1990	69.68
1991	69.56
1992	70.24
1993	70.71
1994	70.52
1995	70.41
1996	70.18
1997	69.78
1998	69.81
1999	68.23
2000	67.06
2001	67.65
2002	69.48
2003	68.96
2004	68.85
2005	69.23
2006	71.13
2007	72.73
2008	74.33
2009	73.72
2010	73.19
2011	73.13
2012	74.67
2013	74.18
2014	74.51
2015	75.71
2016	76.45
2017	77.27
2018	78.11
2019	77.74