Year	Percent
1965	24.26065
1966	23.57724
1967	22.57924
1968	24.6332
1969	22.85914
1970	24.67002
1971	27.15797
1972	26.08575
1973	23.99717
1974	22.79992
1975	25.54303
1976	27.36462
1977	27.80576
1978	28.12203
1979	28.24239
1980	27.13139
1981	28.41413
1982	28.91106
1983	29.30359
1984	30.99343
1985	31.57582
1986	22.72444
1987	20.62604
1988	15.96163
1989	17.76945
1990	17.31353
1991	14.6399
1992	18.31557
1993	12.53477
1994	18.94762
1995	17.61303
1996	23.17734
1997	24.96267
1998	22.46802
1999	20.31853
2000	24.94466
2001	28.28572
2002	27.54592
2003	25.7137
2004	24.22562
2005	26.37059
2006	26.30851
2007	29.60777
2008	32.9219
2009	26.36925
2010	26.95171
2011	31.00423
2012	30.26891
2013	30.03771
2014	30.12672
2015	27.60954
2016	23.41325
2017	19.97625