Year	Percent
1970	64.36025
1971	68.60134
1972	72.65161
1973	78.4636
1974	81.14236
1975	84.7321
1976	97.88743
1977	94.32609
1978	91.61381
1979	90.38116
1980	85.8419
1981	83.76689
1982	81.9618
1983	83.08289
1984	79.16109
1985	80.63293
1986	80.77346
1987	81.15222
1988	79.51709
1989	80.8427
1999	89.80644
2000	92.05299
2001	92.33689
2002	92.7702
2004	93.41257
2005	92.94553
2006	90.40969
2007	94.59897
2008	97.71891
2009	97.71414
2010	93.93404
2011	98.4974
2012	100.55016
2013	99.52673
2014	96.66994