Year	Percent
1965	18.6221
1966	18.37945
1967	20.47872
1968	20.35294
1969	19.14043
1970	18.23816
1971	18.28
1972	17.72647
1973	18.59469
1974	18.13305
1975	21.01079
1976	19.21545
1977	15.83804
1978	12.02707
1979	12.2812
1980	11.86876
1981	9.16201
1982	6.24747
1983	6.62852
1984	10.58209
1985	16.67667
1986	17.15315
1987	16.31903
1988	16.56589
1989	16.7238
1990	16.77283
1991	16.96425
1992	17.37509
1993	24.81857
1994	24.89914
1995	24.285
1996	23.57854
1997	25.66781
1998	25.26654
1999	25.41278
2000	25.40392
2001	25.21598
2002	25.27567
2003	25.20992
2004	24.71676
2005	25.12544
2006	19.80339
2007	19.49281
2008	19.39956
2009	18.51409
2010	18.01494
2011	23.86366
2012	27.13653
2013	26.88283
2014	25.38017
2015	23.57991
2016	22.68549
2017	23.68053