Year	Percent
1965	23.92205
1966	23.7974
1967	23.26688
1968	23.46349
1969	23.94933
1970	24.19893
1971	24.28496
1972	23.70571
1973	22.39445
1974	24.24522
1975	26.06363
1976	24.00773
1977	24.58054
1978	26.3706
1979	34.13617
1980	35.09123
1981	36.05658
1982	31.37962
1983	28.8374
1984	28.15043
1985	27.54135
1986	25.3285
1987	25.90824
1988	27.39915
1989	26.66194
1990	27.30979
1991	32.49602
1992	31.41121
1993	31.14691
1994	30.50286
1995	30.2451
1996	29.51874
1997	28.99962
1998	28.64509
1999	28.40085
2000	30.75187
2001	30.89886
2002	32.5835
2003	33.37059
2004	34.66792
2005	34.14875
2006	36.15474
2007	35.06539
2008	36.21255
2009	35.81645
2010	35.78452
2011	35.95172
2012	39.25131
2013	39.88695
2014	39.89032
2015	36.6302
2016	32.45595
2017	33.75076