Year	%
1970	98.17725
1971	98.1748
1972	98.18566
1973	98.18886
1974	98.4341
1975	98.56645
1976	98.49397
1977	98.54892
1978	98.50548
1979	98.58775
1980	98.68819
1981	98.67134
1982	98.63052
1983	98.43518
1984	98.41508
1985	98.44437
1986	98.48775
1987	98.35648
1988	98.36529
1989	97.88913
1990	98.52038
1991	98.66734
1992	99.23235
1993	99.09463
1994	98.16068
1995	99.34981
1996	99.58568
1997	98.57515
1998	99.7256
1999	99.70984
2000	99.77281
2001	99.68484
2002	99.75568
2003	99.78479
2004	99.74176
2005	99.62259
2006	99.28222
2007	99.26782
2008	99.35197
2009	99.26359
2010	99.29546
2011	99.31053
2012	98.97729
2013	99.1857
2014	99.35638
2015	99.49182
2016	99.55204
2017	99.55609