Year	Percent
1971	97.81138
1972	95.99895
1973	93.88527
1974	93.62383
1975	95.28482
1976	97.23232
1977	99.56092
1978	101.93778
1979	102.45832
1980	99.42602
1981	97.50973
1982	95.79668
1983	96.93272
1984	98.52994
1985	100.40565
1986	104.61856
1987	95.97068
1988	96.85855
1989	94.98219
1992	96.67258
2004	94.95271
2005	93.41604
2006	94.76944
2007	93.07437
2010	91.41119
2011	89.91178
2012	93.3673
2013	91.22765
2014	92.70796
2015	93.66629