Year	Percent
1960	1.21133
1961	1.91177
1962	1.78544
1963	1.45894
1964	1.10806
1965	0.63655
1966	0.28211
1967	0.39659
1968	0.60065
1969	0.12043
1970	0.12385
1971	0.5843
1972	0.84589
1973	1.02117
1974	2.38286
1975	4.77871
1976	3.82022
1977	2.02604
1978	2.03878
1979	2.02506
1980	2.03018
1981	1.88096
1982	1.80041
1983	1.64359
1984	1.55267
1985	1.43036
1986	1.23674
1987	1.10585
1988	1.02257
1989	0.96593
1990	0.88167
1991	0.91909
1992	1.27679
1993	1.45475
1994	1.58597
1995	1.64598
1996	1.66102
1997	1.70946
1998	1.75265
1999	1.79564
2000	1.91611
2001	1.88394
2002	1.67133
2003	1.48482
2004	1.3346
2005	1.26043
2006	1.24383
2007	1.24348
2008	1.17715
2009	1.1094
2010	1.04648
2011	0.83869
2012	0.56424
2013	0.40032
2014	0.39306
2015	0.50006
2016	0.5811
2017	0.57151