Year	Percent
1960	21.28354
1961	16.19828
1962	11.28712
1963	9.50966
1964	14.0801
1965	9.97797
1966	11.65256
1967	15.48552
1968	17.22488
1969	16.13688
1970	19.67942
1971	15.914
1972	15.32664
1973	16.06668
1974	18.03372
1975	11.38234
1976	12.10564
1977	9.65395
1978	7.3345
1979	11.36864
1980	26.31483
1981	24.71721
1982	21.22818
1983	26.33847
1984	39.50251
1985	43.08522
1986	38.62703
1987	46.81774
1988	45.93006
1989	48.12753
1990	43.47703
1991	30.67913
1992	26.50916
1993	16.4203
1994	33.03907
1995	43.12973
1996	45.67306
1997	36.43175
1998	40.60756
1999	29.22785
2000	7.80279
2001	22.45036
2002	25.35048
2003	32.13738
2004	38.53951
2005	42.56932
2006	38.72362
2007	38.83594
2008	43.96489
2009	39.68175
2010	45.44248
2011	46.82708
2012	42.31183
2013	38.25943
2014	37.58598
2015	31.91121
2016	29.15022
2017	34.37044