Year	Percent
1990	67.28
1991	67.67
1992	68.22
1993	68.65
1994	69.03
1995	69.52
1996	69.95
1997	70.57
1998	71.07
1999	71.49
2000	71.31
2001	70.92
2002	70.9
2003	71.72
2004	72.77
2005	73.56
2006	74.27
2007	75
2008	76.59
2009	77.03
2010	78.11
2011	79.43
2012	79.31
2013	79.65
2014	79.81
2015	80.03
2016	80.19
2017	80.48
2018	80.9
2019	80.94