Year	Percent
1961	87.73006
1962	74.12935
1963	72.42991
1964	72.39819
1965	73.00885
1966	71.07438
1967	45.10309
1968	24.77764
1969	21.5
1970	21.53558
1971	23.18145
1972	27.62784
1973	27.80401
1974	16.72825
1975	22.10713
1976	29.26611
1977	32.61513
1978	36.87272
1979	34.40869
1980	29.41291
2010	27.43972
2011	24.13152
2012	25.74034
2013	26.3118
2014	30.56858
2015	39.86129
2016	43.69775