Year	Percent
1975	70.39524
1976	60.60933
1977	78.19027
1978	74.6156
1979	80.88349
1980	84.49105
1981	77.11833
1982	74.11207
1983	70.64936
1984	77.823
1985	76.59178
1986	68.91914
1987	66.12207
1988	58.13012
1989	59.24123
1990	64.28104
1991	54.46246
1992	54.71805
1993	55.59973
1994	42.83297
1995	44.92784
1996	39.16504
1997	39.12232
1998	40.80832
1999	43.72437
2000	39.03866
2001	43.83023
2002	56.63657
2003	54.83077
2004	52.19303
2005	49.84016
2006	42.79662
2007	50.33267
2008	50.66292
2009	47.94941
2010	45.20614
2011	49.01068
2012	45.4638
2013	47.79377
2014	53.56524
2015	52.09028
2016	64.74716
2017	53.98333