Year	Percent
1977	64.51613
1978	63.24533
1979	73.03597
1980	76.88055
1981	64.86144
1982	66.64826
1983	65.88215
1984	63.5383
1985	61.01224
1986	63.647
1987	64.81775
1988	67.89589
1989	75.39347
1990	63.34803
1991	60.77408
1992	58.17107
1993	56.90457
1994	58.75873
1995	55.22355
1996	56.19749
1997	65.83321
1998	66.64925
1999	61.41761
2000	50.58934
2001	48.7068
2002	46.50933
2003	50.10156
2004	52.14729
2005	52.87422
2006	53.33725
2007	61.68995
2008	61.94986
2009	57.49455
2010	57.12891
2011	55.70217
2012	57.927
2013	58.01563
2014	56.79489
2015	54.38081
2016	53.99129
2017	49.06191