Year	Percent
1977	45.58756
1978	44.95317
1979	55.64012
1980	59.8468
1981	68.05222
1982	62.98053
1983	54.45815
1984	48.88788
1985	52.532
1986	56.40369
1987	53.52906
1988	50.72354
1989	48.11685
1990	49.91032
1991	49.58092
1992	44.69491
1993	51.42423
1994	49.80281
1995	49.45091
1996	52.89903
1997	54.20645
1998	56.78025
1999	55.24712
2000	59.63693
2001	53.83992
2002	50.35896
2003	52.69929
2004	53.26507
2005	56.97107
2006	57.59199
2007	57.51874
2008	54.69071
2009	46.80278
2010	49.22975
2011	50.79255
2012	49.46782
2013	50.35284
2014	58.90742
2015	56.7158
2016	52.36255