Year	Percent
1960	10.72294
1961	9.27792
1962	9.43096
1963	9.03786
1964	9.49411
1965	10.51767
1966	10.57821
1967	9.65383
1968	10.11191
1969	10.55617
1970	10.36022
1971	11.22903
1972	10.14711
1973	9.6223
1974	13.03856
1975	12.26865
1976	12.99683
1977	12.5543
1978	10.6601
1979	11.08965
1980	13.12708
1981	14.12104
1982	13.9207
1983	13.29732
1984	14.39322
1985	13.89315
1986	10.91234
1987	9.9374
1988	9.5745
1989	10.11179
1990	10.21976
1991	9.78607
1992	9.69208
1993	9.07786
1994	9.00365
1995	8.9718
1996	9.47907
1997	10.54885
1998	10.52448
1999	9.95176
2000	10.62449
2001	10.2291
2002	11.01822
2003	11.63929
2004	12.97203
2005	14.01244
2006	15.8729
2007	17.49332
2008	17.42404
2009	12.52091
2010	15.03676
2011	14.925
2012	14.54475
2013	15.9154
2014	17.5403
2015	17.58893
2016	16.11915