Year	Percent
1970	91.36842
1971	91.59836
1972	91.81637
1973	92.02335
1974	92.40987
1975	92.60628
1976	92.97297
1977	92.98246
1978	93.16239
1979	93.5
1980	93.50649
1981	93.67089
1982	93.98148
1983	93.98496
1984	94.1349
1985	94.27754
1986	94.55307
1987	94.55041
1988	94.68085
1989	94.68223
1990	94.93029
1991	95.04337
1992	95.15152
1993	95.25504
1994	95.35424
1995	95.55809
1996	95.96413
1997	96.24724
1998	96.52174
1999	96.78801
2000	97.1519
2001	97.5026
2002	97.74359
2003	98.07887
2004	98.40319
2005	98.62205
2006	98.931
2007	99.1371
2008	99.43182
2009	99.71936
2010	99.90766
2011	100.09124
2012	100.36069
2013	100.62389
2014	100.79295
2015	101.0453