Year	Percent
1960	0.26751
1961	0.45324
1962	0.32266
1963	0.26018
1964	0.3156
1965	0.27729
1966	0.30224
1967	0.37216
1968	0.38306
1969	0.4175
1970	0.37978
1971	0.28618
1972	0.2981
1973	0.32228
1974	0.44633
1975	0.58808
1976	0.55018
1977	0.46458
1978	0.34492
1979	0.18075
1980	0.06509
1981	0.00678
1982	-0.05895
1983	-0.15024
1984	-0.2001
1985	-0.18185
1986	-0.17058
1987	-0.1678
1988	-0.15327
1989	-1.08898
1990	-1.03312
1991	-0.00567
1992	-0.03914
1993	-0.11404
1994	-0.13688
1995	-0.13922
1996	-0.17177
1997	-0.20146
1998	-0.23268
1999	-0.28326
2000	-0.25976
2001	-0.22938
2002	-0.28475
2003	-0.28643
2004	-0.22144
2005	-0.19888
2006	-0.15572
2007	-0.15492
2008	-0.1751
2009	-0.15491
2010	-0.22601
2011	-0.28336
2012	-0.51644
2013	-0.27537
2014	-0.26938
2015	-0.23786
2016	-0.29511
2017	-0.33576