Year	Percent
1974	65.66826
1975	68.06777
1976	62.69297
1977	63.01335
1978	68.02849
1979	72.80383
1980	73.68796
1981	68.38043
1982	69.03434
1983	75.39934
1984	77.30317
1985	67.65072
1986	55.387
1987	39.03671
1988	41.41944
1989	42.61481
1990	45.46986
1991	45.13953
1992	36.64975
1993	37.3377
1994	37.04745
1995	44.65135
1996	46.18817
1997	50.1707
1998	43.90391
1999	45.54989
2000	45.74724
2001	43.1874
2002	40.39942
2003	44.11652
2004	48.1227
2005	50.3913
2006	51.9732
2007	50.17965
2008	52.26452
2009	41.22525
2010	44.79056
2011	48.9186
2012	50.35463
2013	48.05242
2014	47.18162
2015	45.83212
2016	47.21459
2017	44.50841