Year	Percent
1990	71.68
1991	71.9
1992	72.14
1993	72.42
1994	72.75
1995	73.13
1996	73.46
1997	73.82
1998	74.17
1999	74.45
2000	74.67
2001	74.79
2002	74.87
2003	74.82
2004	74.78
2005	74.69
2006	74.89
2007	75.16
2008	75.33
2009	75.54
2010	75.64
2011	75.64
2012	75.63
2013	75.59
2014	75.56
2015	75.62
2016	75.73
2017	75.88
2018	76.08
2019	76.31