Year	Percent
1960	98.60573
1961	98.61831
1962	98.60539
1963	98.61352
1964	98.60641
1965	23.1703
1966	19.69895
1967	22.52533
1968	21.02329
1969	21.20225
1970	21.04243
1971	22.19736
1972	20.75418
1973	23.0314
1974	19.88601
1975	19.29877
1976	20.84052
1977	23.40856
1978	23.36814
1979	22.16971
1980	24.65847
1981	24.93134
1982	24.49013
1983	25.21327
1984	24.81086
1985	31.35062
1986	30.90769
1987	31.62032
1988	30.92477
1989	31.32554
1990	30.36958
1991	33.55304
1992	33.03382
1993	35.06108
1994	33.06987
1995	33.17805
1996	33.36949
1997	33.41913
1998	35.23442
1999	34.58437
2000	34.71072
2001	44.4529
2002	43.55295
2003	44.12664
2004	45.17195
2005	45.83415
2006	47.9339
2007	48.77698
2008	49.20432
2009	48.61377
2010	46.39884
2011	45.29399
2012	46.86585
2013	47.55068
2014	48.65457
2015	49.46177
2016	49.96541
2017	51.53593