Year	Percent
1960	35.44304
1961	36.45161
1962	28.47011
1963	27.45455
1964	23.86731
1965	26.73943
1966	19.63109
1967	19.94681
1968	20.82353
1969	20.33983
1970	22.70916
1971	20.24
1972	15.20426
1973	16.39532
1974	21.80258
1975	18.43649
1976	16.04352
1977	11.54708
1978	9.68741
1979	11.16151
1980	9.15477
1981	5.32316
1982	2.98204
1983	5.98898
1984	10.77058
1985	13.58935
1986	20.13559
1987	26.18552
1988	24.06212
1989	24.34325
1990	25.85029
1991	25.5248
1992	28.76764
1993	36.4152
1994	36.76252
1995	32.92665
1996	40.09276
1997	52.99155
1998	46.72819
1999	49.62677
2000	67.24617
2001	64.81284
2002	54.87299
2003	56.6081
2004	60.36701
2005	61.7223
2006	40.72933
2007	40.82923
2008	44.48477
2009	42.30287
2010	45.9011
2011	49.35885
2012	52.80882
2013	47.46325
2014	48.92785
2015	56.12258
2016	48.26291
2017	50.71708