Year	Percent
1960	0.27731
1961	0.67118
1962	0.6737
1963	0.57183
1964	0.47212
1965	0.46401
1966	0.37253
1967	0.35687
1968	0.30476
1969	0.23347
1970	0.21476
1971	0.30479
1972	0.55303
1973	0.40413
1974	0.27355
1975	0.20133
1976	0.18243
1977	0.17374
1978	0.20899
1979	0.29294
1980	0.32104
1981	0.17107
1982	-0.09821
1983	-0.02958
1984	0.09581
1985	0.16319
1986	0.16781
1987	0.14879
1988	0.15818
1989	0.19638
1990	0.23496
1991	0.27341
1992	0.34721
1993	0.31647
1994	0.33253
1995	0.34115
1996	0.33117
1997	0.33277
1998	0.36784
1999	0.40851
2000	0.43362
2001	0.51204
2002	0.7985
2003	0.83436
2004	0.9338
2005	1.04513
2006	1.0898
2007	1.12719
2008	1.13187
2009	1.09511
2010	1.11777
2011	1.11077
2012	1.02211
2013	0.99282
2014	1.07317
2015	1.11135
2016	1.02821
2017	0.95799