Year	Percent
1960	2.15377
1961	2.17843
1962	2.20215
1963	2.23126
1964	2.26787
1965	2.31131
1966	2.35378
1967	2.39749
1968	2.44709
1969	2.5043
1970	2.56645
1971	2.6245
1972	2.68091
1973	2.74159
1974	2.80818
1975	2.87545
1976	2.86841
1977	2.84086
1978	2.90803
1979	3.09212
1980	3.30742
1981	3.59613
1982	3.7301
1983	3.43759
1984	2.63638
1985	1.53812
1986	0.42227
1987	-0.49216
1988	-1.19066
1989	-1.56242
1990	-1.62193
1991	-1.77828
1992	-1.8388
1993	-1.11764
1994	0.62978
1995	2.96603
1996	5.52104
1997	7.35729
1998	7.84971
1999	6.94454
2000	5.3404
2001	3.62927
2002	2.36982
2003	1.72748
2004	1.9128
2005	2.63515
2006	3.45392
2007	3.98074
2008	4.18296
2009	3.97496
2010	3.52106
2011	3.04432
2012	2.70011
2013	2.47367
2014	2.40753
2015	2.44961
2016	2.50636
2017	2.52713