Year	Percent
1960	3.65202
1961	4.74674
1962	4.73717
1963	4.70745
1964	4.52882
1965	4.40638
1966	4.22038
1967	4.12705
1968	3.85157
1969	3.4747
1970	3.0788
1971	4.91854
1972	4.3062
1973	3.90644
1974	3.8112
1975	3.96943
1976	4.10403
1977	4.32086
1978	4.37291
1979	4.15976
1980	3.74611
1981	3.40495
1982	3.0878
1983	2.86418
1984	2.60562
1985	2.4846
1986	2.34644
1987	2.20213
1988	1.09493
1989	1.16231
1990	1.26865
1991	1.4162
1992	1.47691
1993	2.05709
1994	1.94265
1995	1.84663
1996	1.69715
1997	1.53422
1998	1.47485
1999	1.4653
2000	1.53005
2001	1.58002
2002	1.47219
2003	1.3687
2004	1.49013
2005	1.60231
2006	1.56991
2007	1.50352
2008	1.51238
2009	1.47281
2010	1.49509
2011	1.48961
2012	1.51011
2013	1.417
2014	1.28626
2015	1.11011
2016	0.91162
2017	0.75853