Year	Percent
1990	69.56
1991	69.29
1992	69
1993	68.67
1994	68.41
1995	68.14
1996	68.76
1997	69.4
1998	70.05
1999	70.69
2000	71.31
2001	71.94
2002	72.54
2003	73.11
2004	73.67
2005	74.21
2006	74.74
2007	75.11
2008	75.48
2009	75.85
2010	76.22
2011	76.6
2012	76.98
2013	77.36
2014	77.72
2015	78.06
2016	78.4
2017	78.72
2018	78.7
2019	78.69