Year	%
1971	89.24777
1972	89.79592
1973	94.10348
1974	93.19387
1975	92.65647
1976	92.68215
1977	94.63262
1978	94.89988
1979	96.60973
1980	94.03268
1981	95.40311
1982	96.07163
1986	94.72758
1987	95.54621
1988	93.82716
1992	100
1993	100
1999	98.54813
2002	99.21116
2003	98.94538
2004	99.11203
2005	98.15221
2006	99.32581
2007	99.98617
2010	99.07779
2013	100
2016	99.78198
2017	98.22901