Year	Percent
1960	5.39154
1961	3.89301
1962	3.28921
1963	3.18226
1964	3.11207
1965	2.98483
1966	2.86495
1967	2.85993
1968	3.07175
1969	3.21985
1970	3.15762
1971	3.02919
1972	3.10066
1973	2.96457
1974	2.89871
1975	2.90213
1976	2.80569
1977	2.81002
1978	2.66911
1979	2.58228
1980	2.82702
1981	2.77593
1982	2.88327
1983	2.89084
1984	2.86797
1985	2.81705
1986	2.69139
1987	2.75514
1988	2.63915
1989	3.43738
1990	2.54304
1991	0.14106
1992	0.87843
1993	0.85553
1994	0.84373
1995	0.82417
1996	0.81248
1997	0.78824
1998	0.77452
1999	0.75598
2000	0.74248
2001	0.71044
2002	2.18121
2003	2.06027
2004	1.9718
2005	1.82643
2006	1.66223
2007	1.49222
2008	1.43512
2009	1.47329
2010	1.60937
2011	1.78778
2012	1.84838
2013	1.74364
2014	1.64612
2015	1.48476
2016	1.54401
2017	1.54128