Year	Percent
1971	98.78006
1972	96.8672
1973	95.90873
1974	94.89773
1975	95.96579
1976	96.90522
1977	97.71031
1978	100.60149
1979	100.94457
1980	98.08345
1981	96.79008
1982	95.25726
1983	95.30875
1984	97.93143
1985	100.26964
1986	105.65676
1987	95.40954
1988	96.36218
1989	94.12878
1992	96.79543
2004	98.52178
2005	94.74343
2006	97.89699
2007	95.96342
2010	93.42905
2011	91.39411
2012	94.83597
2013	93.74057
2014	93.06398
2015	95.55019