Year	%
1971	63.911
1972	67.54345
1973	69.45674
1974	70.98241
1975	77.54338
1976	80.61413
1977	91.54744
1978	91.11806
1979	94.10181
1981	98.55157
1982	98.7297
1983	98.44118
1984	99.05085
1985	98.7825
1986	99.03986
1987	98.78347
1988	99.0928
1991	98.63049
2004	99.4178
2005	99.28027
2006	97.15436
2010	98.51927
2011	98.41422
2012	99.03985
2013	98.88882
2014	99.56539
2015	97.13093
2016	98.93394