Year	Percent
1960	14.11856
1961	15.50279
1962	12.87534
1963	15.35985
1964	14.68451
1965	15.44923
1966	16.73694
1967	16.55842
1968	16.88314
1969	15.66481
1970	17.06309
1971	15.23517
1972	12.85203
1973	8.79185
1974	21.97343
1975	14.23682
1976	13.595
1977	15.25385
1978	18.7997
1979	18.59926
1980	21.8828
1981	23.28218
1982	11.91995
1983	12.21342
1984	19.25149
1985	17.03264
1986	18.76047
1987	22.15637
1988	22.96902
1989	25.67745
1990	25.78298
1991	23.35938
1992	25.05961
1993	27.9914
1994	25.64375
1995	27.45492
1996	27.84967
1997	27.77917
1998	26.94383
1999	20.86983
2000	22.11675
2001	22.36679
2002	22.33308
2003	21.04102
2004	19.77895
2005	21.84017
2006	20.81582
2007	20.84546
2008	26.81763
2009	21.05837
2010	23.13999
2011	24.64277
2012	26.44944
2013	25.62557
2014	23.23725
2015	23.78036
2016	22.24588
2017	22.05172