Year	Percent
1961	5.08715
1962	3.3402
1963	3.67827
1964	3.18379
1965	5.32142
1966	3.12237
1967	3.24776
1968	2.83803
1969	2.73357
1970	6.45139
1971	6.20437
1972	7.59993
1973	8.04554
1974	9.50214
1975	6.45778
1976	5.62492
1977	5.19871
1978	5.99302
1979	4.11437
1980	5.58063
1981	6.71667
1982	5.35529
1983	3.47278
1984	4.94977
1985	2.963
1986	2.951
1987	2.43695
1988	1.52685
1989	2.96476
1990	2.99968
1991	3.64187
1992	3.47909
1993	2.75708
1994	2.52494
1995	1.81392
1996	0.9862
1997	1.267
1998	0.4419
1999	0.25635
2000	1.36404
2001	1.9471
2002	1.1456
2003	1.30755
2004	1.73972
2005	2.53779
2006	1.89216
2007	2.22118
2008	1.95632
2009	1.88927
2010	0.87305
2011	1.83341
2012	2.05424
2013	1.62389
2014	1.98046
2015	2.31482
2016	1.08885
2017	1.55636