Year	Percent
1960	5.35623
1961	4.77114
1962	5.80578
1963	4.62727
1964	4.87002
1965	4.37237
1966	3.3914
1967	5.13517
1968	2.88004
1969	3.36236
1970	4.04671
1971	3.84742
1972	3.20219
1973	4.56317
1974	3.47651
1975	2.76827
1976	2.70455
1977	2.69415
1978	2.55148
1979	2.99665
1980	2.81725
1981	2.39357
1982	2.26751
1983	2.17798
1984	1.43069
1985	1.88505
1986	1.66732
1987	1.73517
1988	1.77472
1989	1.81288
1990	3.20975
1991	6.13205
1992	3.56815
1993	2.76955
1994	2.7006
1995	2.77731
1996	2.70121
1997	2.57093
1998	2.35829
1999	2.61777
2000	2.71253
2001	2.42726
2002	2.08307
2003	1.87448
2004	1.83652
2005	1.83067
2006	1.83552
2007	1.84269
2008	1.84313
2009	2.4567
2010	1.89539
2011	1.91993
2012	1.92013
2013	1.94322
2014	1.99884
2015	2.06268
2016	2.04386
2017	2.01507