Year	Percent
1990	77.41
1991	77.59
1992	77.69
1993	77.78
1994	77.96
1995	78.06
1996	78.17
1997	78.83
1998	80.42
1999	79.89
2000	79.34
2001	78.77
2002	78.18
2003	77.56
2004	79.94
2005	79.76
2006	80.66
2007	80.06
2008	80.43
2009	78.83
2010	78.82
2011	78.74
2012	79.32
2013	78.89
2014	78.96
2015	81.02
2016	82.84
2017	83.31
2018	82.41
2019	82.06