Year	%
1979	75.08123
1980	75.59428
1981	75.80774
1982	76.68452
1983	78.37519
1984	77.76771
1985	77.77271
1986	78.69494
1987	78.73202
1988	79.62695
1989	80.08327
1990	80.72825
1991	80.09371
1992	80.71509
1993	80.85521
1994	81.92356
1995	82.43527
1996	82.70742
1997	83.72546
1998	84.40064
1999	84.26077
2000	85.44471
2001	85.06883
2002	86.87981
2003	87.80569
2004	88.66745
2005	89.47821
2006	89.09769
2007	90.05049
2008	89.65708
2009	90.66751
2010	90.7976
2011	90.89025
2012	90.38799
2013	91.58602
2014	90.79554
2015	90.94468
2016	90.75194
2017	90.86973