Year	Percent
1967	11.36164
1968	10.22257
1969	11.20363
1970	12.46956
1971	13.41591
1972	10.02927
1973	10.18792
1974	12.72373
1975	9.66119
1976	11.00571
1977	12.7557
1978	11.59798
1979	11.99242
1980	14.80687
1981	13.29978
1982	14.25504
1983	15.92609
1984	19.06437
1985	17.01654
1986	14.49124
1987	15.56173
1988	14.58072
1989	15.81019
1990	15.65359
1991	16.21127
1992	15.6291
1993	15.8535
1994	19.44278
1995	19.56107
1996	18.87148
1997	23.82656
1998	21.25395
1999	20.25099
2000	22.47859
2001	26.31244
2002	28.08745
2003	25.76934
2004	23.67718
2005	22.98887
2006	28.42895
2007	24.15211
2008	25.26776
2009	21.73448
2010	22.83717
2011	22.72618
2012	26.89256
2013	24.92661
2014	22.49171
2015	24.04323
2016	22.91377
2017	22.07976