Year	Percent
1960	1.33039
1961	1.32014
1962	1.29022
1963	1.24282
1964	1.30321
1965	1.32691
1966	1.23436
1967	1.18713
1968	1.13285
1969	1.09928
1970	1.15861
1971	1.24395
1972	1.32881
1973	1.31269
1974	1.40693
1975	1.62596
1976	1.61516
1977	1.52518
1978	1.48308
1979	1.5822
1980	1.66527
1981	1.58061
1982	1.59124
1983	1.49263
1984	1.41244
1985	1.41604
1986	1.42321
1987	1.2823
1988	1.19943
1989	1.10548
1990	1.2035
1991	1.25394
1992	1.20412
1993	1.13923
1994	1.10873
1995	1.01436
1996	0.98993
1997	0.92407
1998	0.82387
1999	0.75068
2000	0.69568
2001	0.70362
2002	0.63405
2003	0.58754
2004	0.56832
2005	0.5409
2006	0.51275
2007	0.50818
2008	0.57575
2009	0.60051
2010	0.57568
2011	0.54047
2012	0.51259
2013	0.49975
2014	0.46542
2015	0.35143
2016	0.3407
2017	0.35678