Year	Percent
1990	77.12
1991	75.73
1992	74.31
1993	73.52
1994	72.76
1995	71.92
1996	71.46
1997	72.6
1998	72.86
1999	73.9
2000	74.2
2001	74.64
2002	74.94
2003	74.72
2004	74.44
2005	74.51
2006	75.09
2007	75.42
2008	75.83
2009	74.77
2010	74.34
2011	74.67
2012	74.96
2013	74.91
2014	75.21
2015	75.63
2016	75.78
2017	76.64
2018	77.79
2019	78.15