Year	Percent
1960	6.55247
1961	5.54384
1962	4.74483
1963	4.32834
1964	4.42252
1965	4.81926
1966	5.39946
1967	5.72794
1968	8.20974
1969	7.71528
1970	7.27122
1971	6.87971
1972	6.68387
1973	6.13113
1974	4.72625
1975	3.64619
1976	2.56196
1977	1.76139
1978	2.31665
1979	4.54436
1980	7.5366
1981	9.86848
1982	11.80092
1983	12.31484
1984	11.60848
1985	10.42721
1986	9.24351
1987	8.41203
1988	7.73787
1989	7.26328
1990	6.85251
1991	6.1398
1992	5.6938
1993	5.40905
1994	5.30513
1995	5.24834
1996	5.44796
1997	5.33579
1998	4.74661
1999	3.56412
2000	2.08451
2001	0.51561
2002	-0.81466
2003	-1.87894
2004	-2.55416
2005	-2.8789
2006	-3.18934
2007	-3.50351
2008	-3.47527
2009	-3.02157
2010	-2.18612
2011	-1.09286
2012	-0.03881
2013	0.68014
2014	0.88898
2015	0.72751
2016	0.47215
2017	0.31353