Year	Percent
1961	8.08228
1962	6.5811
1963	23.42189
1964	16.16517
1965	9.43846
1966	14.95909
1967	8.32571
1968	9.0462
1969	8.02615
1970	11.87873
1971	10.81734
1972	12.96783
1973	20.156
1974	25.38099
1975	22.89729
1976	25.35125
1977	29.16583
1978	17.1069
1979	24.03623
1980	27.60264
1981	22.78227
1982	24.76638
1983	20.39023
1984	22.175
1985	24.90633
1986	29.15158
1987	23.37392
1988	27.7554
1989	24.6818
1990	26.10514
1991	26.18781
1992	22.22595
1993	27.95354
1994	45.35706
1995	18.85096
1996	16.86838
1997	16.83985
1998	14.77305
1999	12.62294
2000	31.76135
2001	6.51845
2002	5.96819
2003	6.82901
2004	7.28303
2005	5.55754
2006	5.77509
2007	5.03976
2008	7.5557
2009	3.40791
2010	3.85626
2011	6.72521
2012	2.98899
2013	1.99271
2014	2.06974
2015	2.45347
2016	4.87831
2017	4.82086