Year	Percent
1990	67.9
1991	68.28
1992	68.65
1993	68.8
1994	68.74
1995	69.4
1996	69.98
1997	70.6
1998	71.23
1999	71.86
2000	72.5
2001	73.12
2002	73.73
2003	74.34
2004	74.93
2005	75.51
2006	75.63
2007	75.72
2008	75.81
2009	75.89
2010	75.98
2011	76.14
2012	76.31
2013	76.48
2014	77.03
2015	77.74
2016	78.56
2017	77.76
2018	78.06
2019	78.27