Year	Percent
1970	64.58601
1971	68.5359
1972	73.31201
1973	79.31943
1974	81.40046
1975	84.33595
1976	100.13103
1977	94.90577
1978	93.11124
1979	91.41685
1980	87.86308
1981	84.73862
1982	84.24266
1983	84.74943
1984	79.50798
1985	81.65409
1986	81.45931
1987	81.69024
1988	79.88703
1989	81.25067
1999	89.52819
2000	91.49069
2001	92.32629
2002	93.02401
2004	93.5055
2005	92.64075
2006	90.21469
2007	94.7719
2008	97.58586
2009	97.20662
2010	93.78079
2011	98.21565
2012	100.20777
2013	98.82576
2014	95.27883