Year	%
1971	72.34165
1972	72.68301
1973	73.82174
1974	75.86262
1975	79.44684
1976	76.56794
1977	78.9875
1978	72.74518
1979	78.56549
1980	79.81357
1981	80.54638
1982	82.48245
1983	83.39808
1984	82.97922
1985	85.26177
1986	84.25216
1987	84.74749
1988	85.71408
1989	87.03784
1990	86.26975
1991	88.79687
1992	89.1984
1993	89.72235
1994	89.80435
1995	89.76996
1996	90.04504
1997	90.06271
1998	90.09203
1999	90.99485
2000	90.89188
2001	91.94226
2002	93.29197
2003	93.56964
2004	91.45898
2005	90.34347
2006	91.70724
2007	91.99947
2008	92.16913
2009	91.6847
2010	91.42098
2011	90.93224
2012	87.8184
2013	88.35717
2014	89.00429
2015	89.69635
2016	90.77706
2017	91.33204