Year	Percent
1990	69.24
1991	70.34
1992	70.05
1993	71.02
1994	72.3
1995	72.62
1996	74.47
1997	74.39
1998	75.89
1999	77.21
2000	78.37
2001	78.85
2002	79.47
2003	79.18
2004	80
2005	80.94
2006	81.32
2007	81.96
2008	81.9
2009	81.17
2010	80.69
2011	80.48
2012	80.72
2013	81.35
2014	81.86
2015	81.97
2016	81.98
2017	82.88
2018	83.22
2019	83.56