Year	Percent
1967	64.50066
1968	64.25608
1969	63.77724
1971	50.64538
1972	67.62256
1973	58.31259
1974	62.75091
1975	64.72176
1976	64.68613
1977	70.48072
1978	72.24031
1979	92.18973
1980	96.61243
1981	83.81681
1982	68.45459
1983	75.46357
1984	68.03615
1985	65.86116
1986	65.4842
1987	60.76956
1988	57.93663
1989	56.87858
1990	53.2205
1991	61.18211
1992	56.49747
1993	64.73228
1994	60.46175
1995	62.00248
1996	55.38218
1997	55.46561
1998	52.20968
1999	48.94092
2000	37.00266
2001	34.21036
2002	36.5859
2003	50.44408
2004	58.28554
2005	69.69021
2006	74.07269
2007	88.77696
2008	88.48348
2009	72.41637
2010	92.21037
2011	95.0732
2012	92.66087
2013	90.61919
2014	81.73351
2015	75.02108
2016	72.29315
2017	75.95207