Year	Percent
1970	85.04785
1971	85.39458
1972	85.94657
1973	86.36884
1974	86.89266
1975	87.29097
1976	87.67877
1977	88.16504
1978	88.62661
1979	89.07741
1980	89.42408
1981	89.85507
1982	90.36885
1983	90.78014
1984	91.27382
1985	91.65839
1986	92.13373
1987	92.50243
1988	92.95367
1989	93.30144
1990	93.73814
1991	94.07338
1992	94.49113
1993	94.90269
1994	95.30387
1995	95.69991
1996	96.098
1997	96.40288
1998	96.70232
1999	97.08481
2000	97.4606
2001	97.74501
2002	98.10834
2003	98.3816
2004	98.64979
2005	98.99666
2006	99.17219
2007	99.50779
2008	99.7563
2009	100
2010	100.23923
2011	100.39494
2012	100.70478
2013	100.85337
2014	101.0761
2015	101.21858