Year	Percent
1990	70.08
1991	70.75
1992	71.31
1993	71.5
1994	71.56
1995	71.67
1996	72.17
1997	72.72
1998	72.76
1999	72.55
2000	72.55
2001	72.68
2002	72.45
2003	72.51
2004	72.4
2005	72.69
2006	72.95
2007	73.51
2008	73.75
2009	73.98
2010	74.17
2011	74.05
2012	74.21
2013	75.09
2014	75.69
2015	76.14
2016	77.02
2017	77.76
2018	79.05
2019	79.82