Year	Percent
1960	3.50878
1961	2.62591
1962	1.8942
1963	1.58748
1964	1.76552
1965	2.25854
1966	2.92834
1967	3.3368
1968	3.60504
1969	3.47959
1970	3.37781
1971	3.31166
1972	3.41226
1973	3.16864
1974	2.5009
1975	1.72142
1976	0.77098
1977	0.11153
1978	0.79026
1979	3.13786
1980	6.457
1981	9.48803
1982	11.42651
1983	11.94864
1984	11.25169
1985	10.08182
1986	8.9066
1987	8.08503
1988	7.41535
1989	6.95349
1990	6.63299
1991	6.17828
1992	5.73315
1993	5.4479
1994	5.3445
1995	5.28676
1996	5.33843
1997	5.19265
1998	4.60387
1999	3.42451
2000	1.95696
2001	0.4246
2002	-0.90481
2003	-1.96944
2004	-2.64358
2005	-2.96605
2006	-3.27856
2007	-3.58946
2008	-3.56105
2009	-3.1071
2010	-2.2708
2011	-1.1792
2012	-0.12651
2013	0.59024
2014	0.79629
2015	0.63687
2016	0.37692
2017	0.21967