Year	Percent
1960	1.95218
1961	1.31529
1962	1.42448
1963	1.34849
1964	1.33778
1965	1.37266
1966	1.30517
1967	1.13314
1968	1.03855
1969	1.15797
1970	1.23893
1971	1.18913
1972	1.01117
1973	0.82733
1974	0.78367
1975	0.89139
1976	0.78499
1977	0.59463
1978	0.61526
1979	0.69028
1980	0.79133
1981	0.68605
1982	0.45856
1983	0.37922
1984	0.39693
1985	0.46633
1986	0.55496
1987	0.63453
1988	0.6461
1989	0.59991
1990	0.6886
1991	0.78803
1992	0.75606
1993	0.69699
1994	0.60294
1995	0.49393
1996	0.4614
1997	0.51477
1998	0.61664
1999	0.66549
2000	0.71477
2001	0.75484
2002	0.63829
2003	0.47181
2004	0.34748
2005	0.23366
2006	0.16061
2007	0.21752
2008	0.38929
2009	0.51428
2010	0.51292
2011	0.46643
2012	0.37006
2013	0.29482
2014	0.35983
2015	0.44322
2016	0.53218
2017	0.6003