Year	Percent
1960	2.54318
1961	2.59851
1962	2.61386
1963	2.54177
1964	2.36259
1965	2.11925
1966	1.8016
1967	1.51554
1968	1.38745
1969	1.47113
1970	1.66738
1971	2.02236
1972	2.24977
1973	1.99544
1974	1.12346
1975	-0.11732
1976	-1.60427
1977	-2.8582
1978	-3.37439
1979	-2.72296
1980	-1.13838
1981	0.8346
1982	2.48665
1983	3.55183
1984	3.80199
1985	3.52248
1986	3.1396
1987	2.93504
1988	2.85965
1989	2.98281
1990	3.21828
1991	3.43548
1992	3.53876
1993	3.5407
1994	3.4228
1995	3.22583
1996	3.02064
1997	2.83378
1998	2.63721
1999	2.43522
2000	2.23606
2001	2.0373
2002	1.85534
2003	1.71376
2004	1.62258
2005	1.57083
2006	1.52772
2007	1.48949
2008	1.47925
2009	1.49945
2010	1.53905
2011	1.58875
2012	1.63048
2013	1.6499
2014	1.638
2015	1.60353
2016	1.56483
2017	1.5299