Year	Percent
1960	2.43222
1961	2.1521
1962	1.88151
1963	1.60434
1964	1.37743
1965	1.1527
1966	0.91872
1967	0.69768
1968	0.50767
1969	0.40297
1970	0.26665
1971	-0.04275
1972	-0.04935
1973	-0.10865
1974	-0.29692
1975	-0.54334
1976	-0.88424
1977	-1.16641
1978	-1.02589
1979	-0.35348
1980	0.70572
1981	1.94726
1982	2.89388
1983	3.21328
1984	2.67569
1985	1.62724
1986	0.38843
1987	-0.61496
1988	-1.18629
1989	-1.07364
1990	-0.45569
1991	0.4031
1992	1.4836
1993	1.84578
1994	1.82114
1995	1.56023
1996	1.24232
1997	1.02644
1998	0.88431
1999	0.82652
2000	0.87213
2001	0.84273
2002	0.22935
2003	0.25331
2004	0.2581
2005	0.26826
2006	0.28373
2007	0.29907
2008	0.31428
2009	0.33468
2010	0.34688
2011	0.36426
2012	0.41317
2013	0.47988
2014	0.54302
2015	0.59731
2016	0.66871
2017	0.7284