Year	Percent
1960	1.23003
1961	0.6441
1962	0
1963	-0.3999
1964	-0.52402
1965	-0.66772
1966	-0.761
1967	-0.69525
1968	-0.55611
1969	0.21563
1970	1.10676
1971	2.16006
1972	2.84314
1973	3.38678
1974	3.52827
1975	3.1335
1976	2.63748
1977	2.39559
1978	2.39627
1979	2.94776
1980	3.45025
1981	4.4099
1982	4.79535
1983	5.02678
1984	4.79714
1985	4.41984
1986	3.80831
1987	3.47316
1988	3.44165
1989	4.02851
1990	4.7419
1991	5.50691
1992	6.05572
1993	6.13864
1994	5.69449
1995	4.91261
1996	4.05193
1997	3.45945
1998	3.48994
1999	4.28322
2000	5.49448
2001	6.72074
2002	7.43061
2003	7.39174
2004	6.68319
2005	5.51853
2006	4.41558
2007	3.5468
2008	2.89416
2009	2.55849
2010	2.44628
2011	2.35005
2012	2.18206
2013	2.06602
2014	1.88795
2015	1.76273
2016	1.62051
2017	1.55236