Year	Percent
1960	2.47235
1961	2.51408
1962	2.5636
1963	2.57174
1964	2.4427
1965	2.37298
1966	2.23391
1967	2.18509
1968	1.95563
1969	1.63273
1970	1.27786
1971	0.85846
1972	0.49094
1973	0.34994
1974	0.49196
1975	0.88048
1976	1.23381
1977	1.5692
1978	1.77756
1979	1.77505
1980	1.56168
1981	1.41774
1982	1.2704
1983	1.20945
1984	1.09707
1985	1.1204
1986	1.10798
1987	1.07861
1988	1.09693
1989	1.16088
1990	1.26825
1991	1.41653
1992	1.47759
1993	1.57149
1994	1.48057
1995	1.40488
1996	1.27483
1997	1.13437
1998	1.0918
1999	1.10215
2000	1.18136
2001	1.24684
2002	1.28484
2003	1.31769
2004	1.29709
2005	1.28732
2006	1.27096
2007	1.21832
2008	1.2399
2009	1.21821
2010	1.25178
2011	1.25852
2012	1.29303
2013	1.21153
2014	1.08991
2015	0.92355
2016	0.73455
2017	0.59157