Year	Percent
1983	78.77815
1984	77.16954
1985	78.13604
1986	78.32124
1987	77.68093
1989	78.29416
1990	79.05993
1991	78.98359
1992	77.73903
1993	78.70178
1994	78.55416
1995	78.12189
1996	78.5073
1997	78.9125
1998	79.31294
1999	79.28637
2000	79.85577
2001	80.23885
2002	80.42796
2003	80.54149
2004	78.9125
2005	80.48029
2006	80.52552
2007	80.94128
2008	81.62681
2009	82.41362
2010	82.33743
2011	82.5123
2012	82.38393
2013	82.48591
2014	82.3223
2015	82.44948
2016	82.70638
2017	83.73544