Year	Percent
1960	4.97757
1961	5.54974
1962	5.9775
1963	6.16858
1964	6.00729
1965	5.64609
1966	5.27233
1967	3.86292
1968	2.70127
1969	2.3254
1970	1.9326
1971	1.49765
1972	1.11585
1973	0.88834
1974	0.85804
1975	0.9844
1976	1.16753
1977	1.83151
1978	2.22208
1979	2.05481
1980	1.80527
1981	1.50826
1982	1.26858
1983	1.13057
1984	1.09859
1985	1.13446
1986	1.22567
1987	0.75263
1988	0.44421
1989	0.40972
1990	0.38028
1991	0.3281
1992	0.31323
1993	0.29392
1994	0.33877
1995	0.39226
1996	0.44966
1997	0.49727
1998	0.54415
1999	0.59472
2000	0.62665
2001	0.66237
2002	0.70173
2003	0.73155
2004	0.74347
2005	0.7508
2006	0.76642
2007	0.83633
2008	0.86693
2009	0.80986
2010	0.74589
2011	0.65067
2012	0.32172
2013	0.13408
2014	0.19876
2015	0.31962
2016	0.48356
2017	0.60518