Year	Percent
1960	0.45433
1961	0.51555
1962	0.58863
1963	0.62801
1964	0.60684
1965	0.54829
1966	0.48043
1967	0.44073
1968	0.43993
1969	0.49528
1970	0.7038
1971	1.18377
1972	1.27224
1973	1.31641
1974	1.31944
1975	1.2897
1976	1.24539
1977	1.21068
1978	1.17098
1979	1.12052
1980	0.88391
1981	-0.33477
1982	-0.39065
1983	-0.42819
1984	-0.43304
1985	-0.41072
1986	-0.3881
1987	-0.3642
1988	-0.35737
1989	-0.35251
1990	-0.40411
1991	-0.63406
1992	-0.6381
1993	-0.6422
1994	-0.64319
1995	-0.64523
1996	-0.63554
1997	-0.63423
1998	-0.64152
1999	-0.66091
2000	-0.6127
2001	-0.27645
2002	-0.29815
2003	-0.30457
2004	-0.28887
2005	-0.2597
2006	-0.22027
2007	-0.19621
2008	-0.17982
2009	-0.18575
2010	-0.20966
2011	-0.16625
2012	-0.11474
2013	-0.06643
2014	-0.01239
2015	0.04054
2016	0.09453
2017	0.14388