Year	Percent
1960	68.49044
1961	61.93268
1962	60.97256
1963	59.90693
1964	55.80103
1965	50.8905
1966	47.6658
1967	41.74933
1968	45.08911
1969	55.70721
1970	58.55903
1971	54.43285
1972	50.80915
1973	57.09096
1974	56.87381
1975	56.96185
1976	52.78711
1977	51.35837
1978	53.184
1979	56.81869
1980	57.54467
1981	55.73556
1982	51.56496
1983	57.17486
1984	55.98854
1985	58.50649
1986	56.43022
1987	54.51833
1988	50.21468
1989	49.78051
1990	51.34236
1991	48.6238
1992	46.04305
1993	44.85464
1994	49.16754
1995	50.72598
1996	53.73099
1997	51.25242
1998	52.20197
1999	50.68807
2000	50.29606
2001	52.7018
2002	48.91948
2003	46.02153
2004	47.2381
2005	48.34799
2006	56.24983
2007	54.0383
2008	65.61976
2009	59.18069
2010	64.03837
2011	69.15823
2012	68.81919
2013	64.42805
2014	60.25901
2015	59.31813
2016	50.01131
2017	49.49421